All There in the Manual: The Paper Trail free DLC offers a lot of details on the setting and characters. Some of the important details revealed include:
The existence of active groups of Conduit Rights activists.
The fact that Fetch's parents are apparently trying to track her down and reconcile with her.
An explanation for why Conduits are still a thing. The Hero ending of the previous game made it seem like Cole sacrificed himself and the Conduits of the world in order to save the majority of the human population. However, playing through Paper Trail reveals that only 90% of conduits were killed.
All Your Powers Combined: Delsin is able to absorb and retain the powers of multiple other Conduits at once. However, he can only use one at once in gameplay and in story. For example, if he's using Neon powers and the player wants to use Smoke, you have to find smoke in the game to change Delsin's powers.
And Your Reward Is Clothes: You unlock various jackets for Delsin by doing things like kicking the DUP out of the various districts in Seattle, completing all of the Cole's Legacy DLC missions and completing all the Paper Trail missions.
Asshole Victim: The Akuras are a gang of Russian bigots who preach conduit genocide in the international district. Murdering Akuras that are minding their own business gives you evil karma, and if you choose to corrupt Eugene instead of redeem him, his evil-karma exclusive quest has you wiping the gang out down to the last member.
Awesome, but Impractical: The Concrete power set. While it can be useful in a pinch and for climbing, it can't be upgraded to the extent that the other powers can and can only be recharged from defeated D.U.P. troopers, meaning that if you want to recharge, you have to go into the line of fire, or drain a blast shard (assuming you haven't found them all yet), since draining those recharges your current power. On top of that, there's no Karma Bomb ability for the power, meaning if you're in a pinch & need to eliminate a large group of enemies fast, you're out of luck, and due this it also lacks the ability to Subdue, making it doubly useless for Good characters, who may even be needed to drop it when the Paper Trail missions want you to make a Subdue/Execute choice to advance the story.
Even more impressive in Paper Trail, which reveals that Augustine arranged for Hank, Fetch, and Eugene to escape while under military custody so she could reinvigorate public support in the D.U.P.
Big Brother Is Watching: The US government's Department of Unified Protection monitors cities with hundreds of surveillance cameras in hopes of finding and neutralizing rogue superhumans. As an added bonus of sorts, all D.U.P. troopers have cameras on their helmets.
The D.U.P. constantly tells everyone to remain calm and trust the agency, despite it being clear their troops are no match for a superhuman like Delsin.
*Delsin decimates an entire D.U.P response unit* Announcement: The D.U.P. is in control of the situation.
In the penultimate mission of a a good karma play through, Augustine broadcasts to the city claims that Delsin is a murderous bio-terrorist and the D.U.P. are trying to save Seattle from him, even though all Delsin has done is try to save people & limit the loss of life.
Book Ends: At the start of the game, Delsin paints all over a billboard featuring his brother. In the Good Karma ending, Delsin makes a memorial for his brother on the same billboard.
Cassandra Truth: The first good karma decision is to have Delsin admit that he's a conduit and try to turn himself in to keep Augustine from hurting the tribe. However, because Delsin doesn't realize his ability is Power Copying yet, he makes the mistake of saying he "caught it" from Hank, which Augustine justifiably doesn't buy as Conduit abilities come from a specific gene & aren't a disease.
Catchphrase: Augustine is very fond of telling people "You disappoint me" (a fact which is used to great dramatic effect later in the game, when Hank sells Delsin to her and she coldly tells him "You didn't disappoint me". She also often exclaims "I'm told that hurts" when using her power to torture people by making concrete grow out of their bones.
Chain Pain: Delsin uses a metal chain wrapped around one of his wrists as an improvised weapon to focus his powers.
D.U.P. agents wear bright white and yellow armor pads, to make them easier to pick out from among the general populace.
Delsin's smoke becomes a lighter shade of red when he's a hero and a thick crimson when he's evil. Neon is either purple and blue or purple and red and Video takes it a step further by determining what weapon Delsin uses based on his karma (a blue sword or red demon claw). Concrete also has the dirt cloud surrounding its abilities change, to either a normal dust color if good, or a soil black if evil.
Delsin's hoodie jacket under his denim vest turns lighter and finally to white once you reach "True Hero" on Good Karma, whereas it turns darker and finally red upon leveling to "Infamous" on Evil Karma.
The Conspiracy: Augustine engineered the escape of the three conduits in Seattle to cause panic and drum up more support for the D.U.P, so Congress wouldn't cut the organization's funding.
Convection Schmonvection: The sole instance of lava Delsin encounters drains his health incredibly fast, but still leaves him plenty of time to escape, and the heat doesn't play a factor; this is justified because Delsin is inside of an MMO (or a recreation made by Eugene's video powers) which usually has exactly these rules for how lava behaves.
Played the first two games? Try not to waste heavy ammo using R1 to fire, it's R2 now, also try not to toss bombs forgetting not only that you don't need to aim, but that button is L2 anyway. You will find yourself doing a dash when trying to drop from a ledge too since circle used to be drop but now it's square, also you may end up swinging the chain when you want to toss a grenade since the toss bomb button moved to L1. Also, the drain button is the touch pad but that's not much of an issue since when you come to a resource to drain you get a prompt.
Neon and Video both have the ability to scale walls with their dash ability while smoke doesn't, so when you want to/are forced to switch to smoke, you'll probably dash into a wall a few times before remembering you need to find a vent or just climb it.
Darker and Edgier: Even though it's still as lighthearted as the previous games, Second Son is much more grounded in reality, getting rid of all the monsters and mutants and changing the setting to the real city of Seattle, rather than fictional cities based on real ones.
One of the button's on Delsin's vest is Sly's logo, and his ringtone is the main theme to Thieves in Time.
Sly's logo appears graffiti'd on numerous walls throughout the game
There's a children's playground with three raccoons as mascots, each with a different element of Sly (his hat, his cane, and a moneybag). Sly has also been drawn on the walls by children, along with his friends Bentley and Murray.
There's a law firm called Cooper & MacGrath (also a reference to previous Infamous protagonist Cole MacGrath) that uses Sly's logo as theirs.
There's a gas station in the game called Panda King Gas, a reference to another Sly character.
Difficult but Awesome: Video relies on misdirection and stealth, rather than brute strength or long-range disintegration like Smoke and Neon, respectively. Used properly, however, you can take down an entire DUP squad without taking a single hit.
In fact, Neon itself can be considered this as compared to Smoke, focusing on precision rather than wanton destruction.
"Cole's Legacy" - A brief series of missions that further establish events that occurred following the ending of inFAMOUS 2, packaged with the various limited editions of the game.
"Paper Trail" - A free piece of DLC included in the game's first patch, that requires the player to further the investigation on the Paper Trail website as part of a meta game that unlocks the next mission in the questline in the main game. New missions were made available periodically over the first six weeks following the game's release. The story of the missions follows Delsin's attempt to track down Celia, the paper conduit mentioned in one of the audio logs in the main game, and provides further background information on the actions of the D.U.P. prior to the start of the game.
"First Light" - An expansion detailing Fetch's past before being caught by the DUP and brought to Curdun Cay. Much like Festival of Blood, it is a standalone release & will not require the full Second Son game to play.
Fetch's life was absolutely ruined by her drug abuse, and her good karma exclusive mission has Delsin helping her take down the leaders of a smuggling ring.
Delsin has the option to aid the police in killing/subduing dealers and destroying their stash for good karma.
The "Purity First" activists you can murder for evil karma are Right for the Wrong Reasons, as they think drug abuse can turn someone into a conduit.
Early-Bird Cameo: Celia, the antagonist of the Paper Trail DLC, is first mentioned in one of the audio logs in the main game and is revealed to be the first Conduit that Augustine brought in, as seen when Delsin copies her Concrete powers.
Elemental Absorption: Delsin can absorb smoke from chimneys, burning cars and tear gas canisters to recharge his powers, just as Cole absorbed electricity in the first game.
Elemental Shapeshifter: Every conduit seems to have evolved to be able to do this now, as opposed to the previous games where only Nyx was shown to be able to do so.
Eleventh Hour Superpower: Delsin only gains the Concrete power at the start of the Final Boss, and spends the remainder of the battle waiting on Eugene to drop in power cores so that it's actually combat viable.
Just like the other entries in the series, doing a good run will make you work harder towards being precise with your shots so you don't accidentally hit civilians, while being evil doesn't care and even encourages you to cause collateral damage.
Some players find the good path easier for the healing benefits found in subduing enemies, which essentially asks for a higher skill-ceiling in exchange for a tactical advantage that evil lacks (evil Delsin can only heal from executing surrendering foes).
Averted with Orbital Bombardment, while Evil builds up much faster (Stringing together enemy kills), it has a timer that will run out and take your progress away unless you continue to fight hostiles. Meanwhile Good has more sources to get it from (healing civilians, non-lethal captures, any good side activity) and never goes away unless you preform an evil karma action, letting you save it for when you really need it.
Averted for the actual progress in the story, unlike the other games which had some tangible payoff like saving you from having your powers dampened or clearing out a harsh fight, there are no points in the story where an evil action is more pragmatic and results in an easier time than the good one, taking the evil way is Delsin doing something purely out of spite.
Evil Makes You Ugly: It's subtle until you hit Infamous karma, but once he's fully evil Delsin's eyes become sunken and have dark black circles around them, and his face and the base of his neck are covered in splotches of black (possibly ashes or bruising).
Fake Video Camera View: The first trailer takes the point of view of video cameras inside different D.U.P. agents' helmets.
Find the Cure: This is the primary reason Reggie and Good Karma Delsin go after Augustine. Augustine tortures the tribe for information by making concrete grow out of their bodies, which can't be safely removed without Augustine's power set. The plan is to have Delsin copy Augustine's powers and use them to save the dying tribe members. Reggie initially also wants to find a way to remove Delsin's powers since he believes being a Conduit is a bad thing. Delsin however doesn't see being a Conduit as a disease.
Foreshadowing: Putting the aiming cursor over Hank when you team up to destroy Augustine's concrete tower causes it to turn red, like the enemies you encounter. This sets up his inevitable betrayal at level's end.
When Delsin supposedly lost his powers, he claims he's going to beat Augustine, even if he has to "throw rocks at her. When it comes time to fight Augustine for the final time, Delsin really does throw rocks at her, thanks to the concrete powers he copied from Augustine.
Averted upon first gaining a new power, Delsin is locked out of any previously acquired powers until he's acquired enough power cores. When Delsin gains the Video and Concrete powers, this actually factors into the story as he finds himself in situations where he would need to be able to use his powers but can't until he's found the first power core.
Averted with the Orbital Drop - When using the attack normally, Delsin has a cocky grin on his face. After Reggie's death at Augustine's hands, using it in the subsequent fight shows a look of sheer rage on his face.
Played straight during the battle on the remains of the bridge as Delsin makes his way to the second island - Augustine places Delsin in a situation where he's going to be forced to reveal his Neon powers to her, as the Smoke powers aren't effective against the enemy. However, if the player is careful enough with their power usage in the battle, it's possible to win the battle without actually resorting to using the Neon powers, but the subsequent cutscene still plays out as if Delsin had used them.
When Reggie's disguising himself as a suspected conduit in order to draw out one of the other conduits, Delsin makes a joke at his expense about shooting at him to make it "look real", and swirls smoke around his hands, even if you went into the cutscene with neon (and it doesn't change to smoke during or after the cutscene either).
Some of the cutscenes don't really work on an Infamous playthrough, with the dialogue not really gelling with Delsin running around & shooting anyone who slightly annoys him. Most notably, is the scene featuring Reggie's death, where his final words to Delsin are that he's so proud of the man he's become.
Good Costume Switch/Evil Costume Switch: The two-headed raven logo on Delsin's vest will change into a angelic white raven if he performs good actions, or a demonic red one if he goes evil. It also tilts with the alignment and his undershirt changes to blacker/whiter.
Good Thing You Can Heal: Delsin was shot in the chest when he awakened to his powers. It didn't do much because of his smoke powers.
Graffiti: One of the first things you do is tagging a large billboard. You can also tag to help with your karma in either alignment, Good Karma stencils being more lighthearted and humorous while Evil Karma ones are typically more mean-spirited and crude. Fetch uses her neon powers to tag as well.
Grey and Gray Morality: Much like inFamous2, Second Son falls into this. Both Augustine and Delsin want to do what is best to protect both the conduits and humanity, but through different methods and goals.
Ground Pound: Delsin can smash into the ground in a cloud of smoke, sending anyone nearby flying.
Guide Dang It: The Paper Trail AR website can edge into this territory. If you've acquired the in-game clues but don't know where to look next, check for any websites listed within the clues and look those up separately (as opposed to the rest of the AR websites that are directly linked to from the Paper Trail website).
Healing Factor: Tacitly justified in the first two games by Cole simply being a powerful conduit, here it's explicitly played straight as fast-healing is straight-up said to be one of Delsin's powers.
All of the conduits Delsin encounters have non-standard powers like smoke, neon or hard light (referred to as "video"), yet the three of them manage to make good enough use of them to be a threat to an army of two-thousand created specifically to deal with supers.
Also, notice how most of these powers are not hard to find at all in a common city environment. Not only do they end up being useful, they have abundant sources scattered around their battlefields of choice.
The audio logs mention that when deciding what power should be granted to DUP footsoldiers that Glass was the runner-up due to its strength and availability, but it was too difficult to master so they chose to go with Concrete instead.
The D.U.P. has ensured that Cole MacGrath went down in history as the Demon of Empire City to justify their Conduit hunts.
Delsin, along with all Conduits, is similarly considered a "Bio-terrorist" by the wider public. The D.U.P. also twist news reports to make Delsin, Fetch and Eugene look like monsters, even if you take the hero path.
Subverted in the Hero path, where the people of Seattle turn against the D.U.P. in favor of Delsin.
Heroic Sacrifice: Reggie allows himself to fall into the ocean while being trapped in concrete, as to prevent the same fate from happening to Delsin.
I Have Your Wife: Hank leads Delsin into a D.U.P. trap because Augustine has his daughter captive.
Implied Love Interest: Delsin and Fetch are implied to hook up partway through the game, though nothing is ever shown.
Not implied in an evil playthrough, where they start making out and more
Minus the pink hair and piercings, Fetch resembles Laura Bailey.
Insistent Terminology: Augustine is quick to correct Delsin when he refers to Hank as a Conduit rather than a Bio-terrorist.
Justified Tutorial: After unlocking a new set of abilities, Delsin has no powers except the Required Secondary Power innate to all Conduits, and has to hunt down blast cores in order to get enough of a boost to unlock new skills. This even affects how the final boss plays out, as you're forced to dodge her attacks until you can get access to blast cores to make concrete not useless.
Knee-capping: With the neon power, it's possible to aim at an enemy's legs to disable them non-lethally as opposed to vaporizing them with a headshot.
Laser Blade: When using his neon powers, Delsin's melee weapon is a sword he fashions out of energy.
Meaningful Name: Delsin has an older brother, Reggie, making Delsin quite literally a "Second Son".
In universe, we have Eugene Sims, a video game enthusiast that frequently plays "Heaven's Hellfire", a fictional MMORPG. His surname could be seen as a reference to his ability to make hard light constructs from video game "simulations".
Bittersweet Ending: More sweet than bitter. In the good ending, Delsin defeats Augustine & exposes the truth of her actions, which leads to the U.S. government freeing the conduits the D.U.P. have imprisoned; the efforts of Delsin, Eugene & Fetch in fighting the D.U.P. leads to the three being regarded as heroes & subsequently leads to conduits beginning to peacefully coexist with regular people without persecution; and having gained the Concrete power that Augustine had used to mortally wound the Akomish, Delsin is able to heal the tribe. However, Reggie still died along the way and the game ends with Delsin making a memorial for him.
Downer Ending: In the infamous ending, the Akomish in Salmon Bay disown Delsin after seeing all the innocents he's murdered ostensibly for their sake, knowing they will die without his help and accepting that fate. In a moment of rage, Delsin performs an orbital drop on the building the tribe is inside, killing them all.
Mercy Kill: The Infamous ending ends with Delsin using an orbital drop to kill the Akomish afflicted with the concrete after they disown him and refuse to accept the cure for the disease. This is probably just out of anger, however.
Not Staying for Breakfast: In both karmic paths, Fetch has to catch up to Delsin through a phone call later in the day when she wakes up herself. Good karma path is a bit ambiguous on the whole Did They or Didn't They? part, evil leaves very little for speculation.
Not Quite Flight: Each of Delsin's power sets allow him amazing vertical maneuverability, but none of them allow free, sustained fight. Delsin can fall in style. In many styles. However, he can't really fly.
Or, as Reggie says, "you can fly... in three different languages!".
Obliviously Evil: During a gameplay trailer a D.U.P. agent voices his lack of understanding as to why any civilian, let alone a group of them, could possibly treat them like the bad guys when said agents are trying to "protect" them from the "bio-terrorist". You know, despite the fact that the D.U.P. is constantly watching EVERYONE, Conduit and Human, and taking away just about any form of privacy that the civilians originally had.
Ominous Multiple Screens: The Department of Unified Protection's Seattle HQ has a wall of monitors that allows them to keep tabs on the entire city.
Order Versus Chaos: The D.U.P. represents order at the cost of freedom; Delsin represents the opposite.
Pacifist Run: It's difficult to get through a game with zero casualties but most of your primary powersets come with completely nonlethal options, provided you start off Good (going Evil increases your general lethality). A smoke shot to the head makes enemies cough and an easy target for a nonlethal takedown, as do several grenade options. The Neon beam attack shows you lethal and nonlethal weakpoints on enemies by default so you can quickly zap out their legs and be done with it, and so on. Even better, your good-style Karma Bomb that charges up from subduing enemies nonlethally is itself nonlethal, just binding them all to the ground (even though it blows up everything else).
Playing with Fire: Delsin gains the power to manipulate smoke and flames, much like Nix from InFamous 2. Though he can burn or blow up stuff with cinder missiles, his smoke can also be utilized nonlethally to stun and confuse enemies.
Possession Implies Mastery: Getting new power cores to unlock new powers gives Delsin a video of him using his new powers. Somehow he just instinctively knows how to do all this stuff the moment he can do it.
Power Copying: Delsin is actually a Conduit with the power to absorb the abilities of other superhumans through contact. All Conduits focus on manipulating Elemental Absorption: his element is Conduit.
Revision: Second Son establishes using the RFI at the end of InFamous 2 didn't kill all superhumans as Cole and Dr Wolfe feared, just a lot of them.
Retcon: Seems to be the case as far as the way Conduits function goes. In inFAMOUS 1 and 2 it seemed to be heavily implied that the vast majority of Conduits exhibit various types of Psychic Powers (most commonly telekinesis, judging by the amount of them who could do it to some degree), but by the time of Second Son it would seem like they've all got various types of (loosely defined) elemental powers. Furthermore, only Cole actually had to "drain" his "element" in order to use his powers in the first two games (which was explained as his powers literally relying on the electricity his body stores), whereas in Second Son having to drain elemental power from the environment appears to be the standard, and Elemental Shapeshifting seems to be an innate ability now that's useable by all conduits, while in 1 and 2 only Nix was shown to be able to do so to that extent.
Rewarded as a Traitor Deserves: Hank's betrayal of Delsin and the others at the cost of freedom backfires when the D.U.P commander he calls for pickup turns out to be especially racist and sends his men to kill him rather than give him asylum. However, whether or not he dies is up to you when Delsin catches him.
Ridiculously Fast Construction: Augustine's concrete powers allow her to create citadels of stone (then apparently someone else spraypaints a few yellow lines here and there).
Roaring Rampage of Revenge: After Augustine kills Reggie, Delsin goes berserk and begins punting her like a football after knocking her defenses down, all the while screaming at her over what she's done, and when she calls soldiers to aid her all of his attack are fatal, even if he's good karma. This also extends to Henry, but if Delsin is good karma, he lets him go and calms down before going to assault Augustine's base.
Scenery Gorn: The bridge to Seattle, demolished by the D.U.P. and still collapsing as Delsin crosses it.
Serkis Folk: The game uses various actors' motion capture performances to create its in-game cutscenes.
Sequel Reset: Second Sonside-steps the canon ending of InFamous 2 and returns to the previous status quo, with new Conduits and a new anti-Conduit task force appearing. As it turns out, Cole's use of the RFI only killed most of the world's Conduits.
Sequel Hook: In the good ending, all the conduits in Curdun Cay are set free, but considering that some of them (like Hank) probably needed to be in there, this could have repercussions later. In the Infamous ending, Delsin decides he's going go after Curdun Cay himself to not just free the conduits, but load up on their powers.
Sigil Spam: D.U.P. has their facilities and vehicles covered in their logo and distinctive black, white, and gold color scheme. This also helps players identify the Everything Is Smashable Areas.
One of the Good Karma stencil art pieces has a D.U.P. trooper having his pants pulled off by a dog, reminiscent of the classic Coppertone girl.
An Evil Karma stencil art piece has the Space Needle-headed Rock 'Em Sock 'Em Robot bopping off the head of a D.U.P. trooper.
One Evil Karma stencil image has an old man about to mow over the heads of several buried D.U.P. troopers, reminiscent to a scene from Caligula.
Scattered throughout the city are advertisements for a Phoenix Jones movie, in reference to the real-life "superhero" based in Seattle.
A possible reference to Death Note is the D.U.P. operator who Delsin keeps pestering refusing to give him her name when asked.
Operator: I am not going to tell my name to some bio-terrorist! You might have... name-controlling powers or something.
A stuffed toy of Knack can be found in the Longhouse Hospital at the beginning of the game.
Ship Tease: The romantic subtext between Delsin and Fetch isn't exactly subtle.
Sex Is Evil: And while they seem to spend the night together regardless of karma, Corrupt!Fetch throws all possible subtlety out of the window.
Shown Their Work: The raven imagery associated with Delsin is evocative of Coast Salish mythology.
Sinister Surveillance: The D.U.P. has cameras all over the city, constantly looking for Conduits like you. They even put them on D.U.P. troopers' helmets.
Smash to Black: Used in the Infamous ending right before Delsin destroys the longhouse.
Smoke Out: Delsin can create a clouds of smoke to obscure enemies' view, allowing him to catch them by surprise or sneak away.
Spanner in the Works: Delsin's ability to absorb Core Relays is the primary reason Augustine's careful planning falls apart.
So Proud of You: Near the end of the game, Reggie tells Delsin that he is proud of the man Delsin has become. All the more powerful because these are his last words.
Super Drowning Skills: Delsin's fine if he lands in the water, usually just making a comment about how cold it is. But the game freezes you in place and forces you to hit the touchpad to return to shore. Exceptions are in exceedingly dangerous areas like the collapsing bridge or the D.U.P island you raid near the game's end, but in this case it just cuts to black and puts you at the last failed jump.
Super Smoke: Your starting power is the ability to control and transform into smoke.
Superpower Lottery: Conduits all have different abilities based on personality or environmental factors.
Video Game Cruelty Potential: Of course you can kill people for evil karma. What did you expect? And if you're evil and you start performing good deeds like healing people or restraining enemies the game basically tells you to stop being good.
Well-Intentioned Extremist: As it turns out, Augustine heads the D.U.P. and imprisons Conduits because she's convinced that it's the only way to stop them from being persecuted and killed by the military.
When All You Have Is a Hammer: Despite that they all draw from the same power well, concrete, the D.U.P. troops and Augustine have a wide variety of applications for this power. Some guys can jump by creating concrete wedges under their feet, or cling to wall by making a temporary platform. Some guys armor themselves up, and there's a "wizard"-like buffer unit who tries to imprison you in concrete while shielding others with floating rocks. There's a very large mid-boss who uses rotating pylons of stone and concrete torpedoes that rip through the ground towards you. The troops also use their powers to build military fortifications all over the city. Augustine herself is basically Magneto with rocks, having all these powers and the ability to turn herself into a gigantic morphing rock monster by surrounding herself with concrete.