Abnormal Ammo: Some zombies will resort to pulling their head off and throwing it at you.
Adaptation Dye-Job: As this continuity has Sypha as the mother of Simon, she's gone from a blonde to a redhead.
Adapted Out: Fans of the series may remember the team of Trevor, Sypha, Grant, and Alucard. In this game... Sypha gets Demoted to Extra, appearing only as Simon's mother and never being hinted as having any special ability at all. Grant DaNasty is briefly mentioned in a scroll the character can find, not actually appearing at all. And Trevor and Alucard are merged into a single character.
Anachronic Order: The game starts out following Gabriel a year before Lords of Shadow, then jumps ahead 57 years to Simon's scenario, then Alucard's scenario takes place concurrently with Simon's, then it jumps back 30 years to Trevor's scenario for the end-game.
Another Side, Another Story: The game features four successive playable characters: Gabriel Belmont, Trevor Belmont, Simon Belmont, and Alucard. For the most part, they share the same gameplay mechanics, and other than Gabriel, any exploration upgrades are passed on to the next character's story, even if it doesn't make much sense chronologically. They also share Character Level, health, magic, and subweapon upgades, although their arsenal of magic spells and subweapons differs between each character.
Anti-Grinding: Character Levels are not important, and only unlock new whip skills. Plus, enemies don't give off a lot of experience, and all characters share the same level. HP, MP and ammo-hearts are instead upgraded with Upgrade Artifacts.
An Axe to Grind: One of Simon's two subweapons, plus the main weapon of the Executioner.
Bag of Spilling: Subverted with Gabriel, whose story takes place before Lords of Shadow. Played straight with Trevor, who can Double Jump and Wall Jump before he turns into Alucard, where he has to re-obtain these skills, although he can't glide after a double jump as Trevor.
As detailed under Elemental Rock-Paper-Scissors, you not only fight Dracula the same way you fought Satan in the previous game, but you also have infinite magic for the duration of the battle, and getting hit by any of his elemental attacks when using the same element does no damage to you.
The device Gabriel uses to trap the Daemon Lord in the prologue is a much, much smaller version of the contraption that shows up in the Reverie DLC as the gateway to the Forgotten One's prison.
Call Forward: Dracula uses his Blood Whip from Lords of Shadow 2 in his fight against Alucard, and his Void Sword and Chaos Claws from the same game in the final battle.
Cel Shading: Used in the cutscenes. Regular gameplay uses normal shading.
Chaos Architecture: Both subverted and played straight. Whilst Simon and Alucard share some areas with each other, most of the areas they visit aside from the theatre and laboratory are unique to their path.
Played straight with Trevor, who visits most of Simon's areas in his path, and features a lot more death traps.
The Chosen One: Said prophecy states the Belmont Clan are the only ones capable of destroying Dracula.
Composite Character: Like the previous game, The Reveal here is that two characters are actually one character in this universe. Alucard is a combo of classic Alucard and Trevor Belmont in this continuity.
The Dog Bites Back: When the Watchman has been defeated by Simon, he summons his Scavens one last time. They promptly eat him. Subverted to a degree when it turns out that this is what turned him into the Reaver, which is what he might've been intending to do to begin with.
Alucard obtains the ability to jump again while in the air after defeating the Daemon Lord, via a pair of wings.
Trevor has one from the get go, thanks to some enchanted boots.
The Dragon: The Succubus serves as Dracula's second in command.
The Daemon Lord seems to become one for the Toymaker.
Elemental Rock-Paper-Scissors: In Trevor's final battle, you fight Dracula the same way as you fought Satan in the first game - by activating whichever type of magic he's not using and switching to the matching type when he uses an unavoidable shockwave attack.
Evil Costume Switch: Dracula now sports more demonic clothes, after his Face-Heel Turn in the first game. Trevor also goes from a blue coat and silver boots to a set of black armor after becoming a vampire.
Fake Difficulty: The Boss Rush added into the HD version tends to suffer from this, partially because there's no checkpoints of any kind which can be expected since there hasn't been any in any of the earlier games, but more importantly because you don't gain back any health at any point after beating the bosses and the only one with any form of reliable healing is Trevor, who is the last character.
Fallen Angel: The Vampire Knights all have black feathered wings.
Famous Last Words / Apocalyptic Log: The bodies of the Brotherhood adorn the castle, and their last thoughts are embedded on a magic scroll they carry with. Most of these are fluff, but some of these contain hints on certain parts of the game and they all give you a decent amount of bonus experience.
Alucard also has one when he remembers his failure to defeat Dracula as Trevor and decides to finish what he started by killing his father.
Hint System: Alucard's two big puzzles have this, though with each hint you take, the puzzle is worth less experience, and doing them without any hints is needed for an achievement/trophy in the HD version.
I Know You Are In There Somewhere Fight: In the first boss fight with him, Dracula enchants Simon and tries to force Alucard to fight him. Alcuard refuses to hurt Simon at all and shouts "No Way" and other refusals anytime you press any attack button, forcing you to parry his attacks and quickly grab him before he recovers.
Indy Escape: In the Belfry area, some hunchbacks send a giant bell rolling after Trevor.
I Never Told You My Name: Dracula already knows Simon is a Belmont because he overheard Alucard talking to Simon. It's one of the first hints about who Alucard is.
Interquel: Bridges the gap between the main events of Lords of Shadow and its epilogue.
Letting the Air out of the Band: When Simon collects the Combat Cross from a glorious pedestal with light cast on it through a beautiful church window, the marvelous "Item Get" fanfare builds up — and the Necromancer steals the Combat Cross and it goes warbled.
Press X to Not Die: The 3DS version features numerous quick-time events. The HD version removes many, though not all, of them; mostly the ones for Alucard's wolf doors, Trevor's stone doors, and the ones for finishing off bosses.
Prophetic Names: Gabriel, who loved mountains, gave himself the last name Belmont because it meant "Beautiful Mountain." His grandson, Simon Belmont, ends up being raised by mountain folk years later.
The Quiet One: The Spectre of the Mirror can talk, and he does so quite normally in Trevor's path. (Getting a combat cross to the face and breaking off a large chunk of his mask because of angry smoldering generic rage courtesy of Trevor probably shut him up.)
Recurring Boss Template: The Necromancer fights nearly identical to the Grim Reaper. Considering his master was Zobek, The Lord of the Necromancers (and alluded to be Death in Lords of Shadow), it makes sense.
Dracula, as well, fights a lot like Satan in Lords of Shadow; this is probably because at the moment he is the Prince of Darkness.
Stranger Behind the Mask: The Lost Soul. You've been wondering who he is the whole time... and he's nobody. He's just a personification of Fate. They don't even tell you this in the game — it's in a bestiary entry unlocked when you win.
Summoning Ritual: Instead of Dracula (who's usually the target for these things in Castlevania games), it's the Daemon Lord in Trevor's path.
Sympathy for the Devil: In his final moments, Trevor pities Dracula after the Mirror of Fate shows him why he turned evil.
Tag Team: Simon and Alucard team up against Dracula.
Take Your Time: Both Simon's and Alucard's campaigns run simultaneously, but you can take all the time in the world before you go to the throne room, and fight the Final Boss.
Particulary egregious is when playing as Alucard, and you have to solve puzzles with blocks or mirrors whilst Simon is fighting for his life.
This Looks Like a Job for Aquaman: None of the three playable characters run into any of the obstacles that the others must get past, aside from the grappling hooks Simon can't use with his leather whip.
Trailers Always Spoil: Trailers and promotional material make it clear from the start that Trevor fails to stop Dracula, leaving Simon to finish the job years later. Not that Dracula returning to menace a new generation is a surprise.
Dracula in Simon's chapter. Dracula is the last boss faced in Trevor and Alucard's chapters, but he only appears in Simon's chapter in the ending cutscene, the Succubus being Simon's final boss.
The Daemon Lord's battle with Trevor is built up pretty heavily over the course of the game. It turns out to be a few QTEs. Same goes for the Lady of the Crypt's impressive true form.
The Toy Maker is a pretty huge presence throughout the game. His backstory is built up through various item and bestiary descriptions, as well as Brotherhood knight scrolls during the course of the game. Alucard even has to navigate through areas named after him, and all 3 characters must fight his creations. Yet, he goes not only unfought, but unseen until the very end of the game.