Harry Potter and the Natural 20 by Sir Poley is an on-going Cross Over fanfic that combines Harry Potter and Dungeons & Dragons.The premise is Milo Amastacia-Liadon, munchkin and Wizard with capital W, hailing from Myra - City of Light! City ofMagic! - turns up in the world of Harry Potter through a Summoning Ritual by Lucius Malfoy. After teaming up with the three protagonists of the Potterverse, he takes on the many dangers living at Hogwarts School for Witchcraft and Wizardry can bring - in his distinct and hilarious way.Currently in the third year and the author has indicated wanting to do all seven books.
Harry Potter and the Natural 20 provides examples of:
There was an evil forest. An animated tree (a disguised Treant, possibly?). A lake with mermaids. "This place is awesome," he said. The amount of XP he could get just from random encounters in the school grounds alone... it suddenly made sense to him how such a school could be an effective way to gain power. This place was clearly, really, incredibly, obviously, brilliantly dangerous.
Ascended Extra: Hannah Abbot turns from Hufflepuff to Gryffindor and get significantly more screen time.
Authority Equals Asskicking: As he is now in a society of wizards displaying powers far in excess of what he feels should be possible, Milo can be forgiven for assuming that this trope is in effect (how else would the man in charge stay in charge?). However, it doesn't change the humor in seeing him refer to Minister Fudge by increasingly opulent titles as his terror at possibly offending (what he thinks is) one of the most powerful beings in the hemisphere rises.
"He was back in the hospital wing after being mauled by (and they wouldn't have believed it if there hadn't been twelve witnesses) a Flobberworm."
Can't Catch Up: Not true in the slightest, yet Milo maintains a low-key but constant struggle to consciously avert this trope by tailoring his build to the campaign he’s found himself in, and occasionally turns contemplative about whether or not he’s succeeding.
Celebrity Paradox: The Muggles think that Gilderoy Lockhart looks a bit like Kenneth Branaghnote the actor.
Chain of Deals: Milo gets Galleons from Harry, then gives them to the goblins at Gringotts for British pounds, then gives those to Hermione to give to Muggle truckers for road salt, and then uses that road salt in his Item Crafting. See Money Multiplier below.
Character Alignment: Milo theoretically has the ability to detect evil at will from his Rainbow Servant prestige class, though it's still unknown if people in the Potterverse even have detectable alignments.
As a munchkin wizard, Milo is True Neutral at the start of the story, but he develops into Neutral Good as it goes on. invoked
Character Level: Milo brings this to the fore, with special attention paid to the decision making process involved, and the compromises he has to make between what he wanted and what's realistically a good choice.
Chronic Hero Syndrome: Milo has a bad case of it — to the point he doesn't even have a reason for this. It's just who he is.
Comically Small Bribe: Milo tries bribing a Muggle police officer with 500 pounds of salt, because he doesn't have any pounds and the Player's Handbook states that transactions can use "trade goods" when money isn't available.
Combo Platter Powers: He doesn't have access to them all yet, but Milo will eventually have the domain powers of Air, Law, and Good, which include casting Law and Good spells at a higher caster level and turning earth creatures.
"And then I will find you – there's magic that will let me do it instantly – and then I will kill you. Slowly. And then I will rip out your soul and trap it in a shiny rock, which I will then hide on a moon – which moon, orbiting which planet, orbiting which star, in which galaxy, I will leave to your imagination – so you can never be brought back."
Crazy-Prepared: What Milo has in his Belt of Holding include fifty feet of silk rope, a grappling hook and... a bucket, the last of which he's kept in his Belt for three years without it being any use at all and finally served as tinder. Of course, if Milo had waited a little longer...
Crippling Overspecialization: These sorts of spells are referred to in-story as "use-impaired". They're certainly useful in the particular situational contexts for which they were designed, but those are so inherently rare that it's not, as a general rule, worth the effort of preparing them.
This is side-stepped through several ways of sacrificing power for versatility, i.e., robust spells that can ape weakened versions of the more thoroughly specialized.
Cryptic Conversation: Milo bluffs his way through a few of these with Draco Malfoy, without ever figuring out what it was really about. To be honest, no one could have guessed what crazy plot Malfoy had in mind.
Curb-Stomp Battle: Bellatrix Lestrange versus Gerard, Wellby, Zook and Thamior the Thaumaturge ends with the former doing the stomping.
Even Evil Has Standards: Played with. Even the Slytherins were shocked when Milo proposed to use (well-armoured) Muggles as meat shields.
Evil Is One Big Happy Family: It’s a plot point in the first book that Milo stumbles over his inability to grasp an aversion of this. Namely:
Snape and Lucius are working together to get Milo off of school grounds alive so his Summoning Ritual can be reversed (even then, and unknown to Milo, Snape only does so to maintain his cover as a Death Eater, and is ultimately merely ambivalent to Milo’s fate).
Draco is not working for his father and has his own ridiculous plots to carry out against Milo.
Voldemort does not want Milo dead, merely in constant mortal peril, so that he may grow stronger and achieve the ability to raise the dead, an ability more valuable than any Philosopher’s Stone.
Quirrell does not want to be the Dark Lord’s slave, but cannot risk disobeying him even in conscious thought.
In addition, as momentarily foreshadowed in the first book and made explicit in the text of the second, Lucius adds the wrinkle that he does not truly want the Dark Lord to return, as his current methods are more efficient at achieving pureblood goals, and is only attempting to bring Voldemort back to maintain the pretense of effort in order to better control the former Death Eaters.
I doubt he's even human. We may have accidentally created some sort of... Homunculus. An artificial human. There's no telling what it might do.
Fighting from the Inside: To the surprise of both Milo and Dumbledore, Quirrell. At the very least, he enacts a plan to save himself from possession that he could at no point have thought of on a more than subconscious level. The ambiguity of his allegiance leaves his ultimate fate unknown.
Gambit Pileup: Between the plots of Lucius, Quirrell, Snape and Draco, it's no surprise Milo can't fit the big picture in his Plot Chart.
Avada Kedavra to the D&D verse. Seriously, an instant-death spell without so much as a check?
Also, Harry Potter world characters are apparently exempt from the D&D turn order rules; they can cast spells more often than once every six seconds and don't have to win Initiative to act first.
On the other hand, D&D magic is extremely powerful in general. From suppressing the Imperius with Protection From Evil to (in theory) duplicating Raise Dead and Resurrection with Limited Wish / Wish, Milo holds enough potential to completely change everything in the Potterverse.
Game-Breaking Bug: Taking an action that would normally cause one of these instead invokes Rule Zero to come along with a karmic punishment, amounting to the same thing without destroying the universe. Milo risks it and pays the price.
Mordenkainen is worried that something like this will happen to him should his master die, as there is no record anywhere of what happens to a Familiar once their master passes away.
They turn back into a normal animal until their master returns to life.
Genre Savvy / Wrong Genre Savvy: Being the munchkin he is, it's no surprise Milo sees where the plot is railing him into. Though most of the time he is also hilariously wrong about people's plans.
Milo also has a pleasant inversion: WrongGenre Blindness. Several features of his build, most notably his high charisma/low constitution, are suboptimal in his home campaign but useful in the Potterverse.
Snape often shows signs of being Dangerously Genre Savvy, such as using flour to detect an invisible Milo when the standard methods for finding invisible people fail.
A God Am I: What Milo might become if he ever gets his hands on a Candle of Invocation. Also, what he sees in the Mirror of Erised.
Gone Horribly Right: Upon gazing on the Mirror of Erised, Milo finds out what happens when all your dreams come true...
Gravity Master: If he hadn't had Feather Fall, Milo would have been dead in the first chapter.
Milo also picks up Levitate early on, and puts it to good use.
The Guards Must Be Crazy: Exactly what Milo was thinking as he escaped Malfoy Manor for the second time. Though of course this was carefully orchestrated by Snape.
The Gunslinger: Harry, he's apparently so fast that he can reliably beat Milo's Initiative, since Milo's total bonus is +6, Harry seems to have an effective dexterity of over 18 and the equivalent of the improved initiative feat.
In the D&D world, Bellatrix Lestrange isn't subject to the turn order rules at all, letting her act far faster than nearly anything in the Planescape.
Heroic Self-Deprecation: For all that he enjoys making full use of his hard earned magic, Milo will still get down on himself for perceived flaws compared to the native wizards, eventually vowing to do his Class proud, regardless of how underpowered he thinks he is.
Recently, he's turned to lamenting not being a Druid.
Hufflepuff House: Great people. Nothing against them. Perfectly respectable house.
Lucius, for his part, merely thinks of the creature as a Homunculus.
On the flipside, Milo is wholly unsettled by the slow realization that Potterverse wizards learn gradually over time, rather than in discrete increments like literally every other living thing in his world.
And while he hasn't learned of it yet, this will presumably be his reaction to learning that Lockhart gained his overwhelming backstory by stealing those of others.
Humans Are Cthulhu: Judging by comparison to Milo's stats, Harry and Hermione seem to exceed D&D's theoretical human maximum in Dexterity and Intelligence respectively.
I Know You Know I Know: Snape deliberately maneuvers Milo into spinning his wheels through one of these with his life on the line. He finds it hilarious (which it is).
Fiona explains to Travis why they have to knock at Mrs. Figg's door despite knowing she's out with a brief usage of this trope.
Travis: She won't answer. She's not home. We saw her leave not half an hour ago.
Fiona: I know that. And you know that. And all the nosey neighbors of Little Whinging know that. But they don't know that we know that. So we knock, first.
I Need You Stronger: Once Voldemort finds out that a) Milo directly grows in strength from mortal peril and b) he can raise the dead with sufficient strength, it becomes a priority to send a constant influx of strife towards the party.
Insistent Terminology: Myra - City of Light! City of Magic! - is always referred to with its appellation.
In general, Milo runs on the heuristic that anything with more than two adjectives describing it is capital "I" Important, and therefore to be placed on the Plot Chart, at different points deducing both Quirrell's and the Rememberall's Importance directly from this technique.
A large portion of the second part of the story is essentially about how Milo's reliance on the Law can fail or cause as many troubles as it solves. Due to his interference in the story, many of the plot points of the second book are greatly altered or removed in such a way that his Genre Savvy behavior tends to backfire.
Milo had been bored in the past—occasionally. It was a rare occurrence, and nothing particularly concerning on its own. More worryingly, however, was that at some point he'd dropped out of a timeskip. Milo's awareness of the weather confirmed it. There were only two reasons for such an occurrence: flavour and drama. Were the first option the case, the timeskip immediately would have resumed after some humorous or character-establishing moment, followed by another—say, at dinner, where the NPCs would discuss foreshadowing. But Milo was still experiencing time at a one-to-one ratio, barring this from being the case.
Something was awry.
Amusingly, following this passage and continuing on into the next chapter Milo becomes increasingly distressed and paranoid that absolutely nothing (to his mind) is going wrong.
As in canon, Lockhart's first test is a lengthy series of petty details about himself, meant to illustrate one of his character traits: his narcissism. Milo, not catching this, takes each detail as a full-fledged character trait of its own. This worries him greatly.
Level Drain: One of Milo’s greatest fears, and the indirect cause of his subsequent fear of undead.
Limited Move Arsenal: Being rather proud of his many clever workarounds to avoid the common problems of having only so many spells he could possibly use at once, Milo is upset to discover his friends have no such limitations. He gets over it, eventually. Mostly. Kind of.
Linear Warriors, Quadratic Wizards: In effect between Potter!Wizards and D&D!Wizards. The advantages held by Potter!Wizards, namely being able to ignore turn order, are available straight from learning magic. On the other hand, as Milo increases in level he will access Epic magic far beyond anything anyone at Hogwarts can learn
Lonely at the Top: Milo realizes this would be his likely fate if he continued acting like a munchkin. When you only interact with others for the sake of their assistance (like he does at the start of the story), once the best assistance can only be provided by copies of yourself, there’s little reason to have anyone of real importance in your life. See Gone Horribly Right above.
Loophole Abuse: Milo’s bread and butter. So far he’s gone nearly a week without sleep, mentioned he’s effectively immune to alcohol, and created a system of writing that only he and his Familiar can understand.
Milo: When you people are taught to count, we're taught to abuse poorly thought-out rules.
Hermione shows an off-hand adeptness at this that leaves Milo speechless, completely revolutionizing Milo's brand of Divination twice over in seconds, without even stopping to think first.
Hermione: Sometimes it just takes an outsider's perspective.
Master of Illusion: Not in an absolute sense, since he only uses a fairly low-level spell for the effect, but Milo puts the ability to make soundless, scentless, touchless visual projections to great use.
Medieval Stasis: Milo is horrified to realize that magic is keeping his world stuck in this.
Memory Gambit: Fiona Smythe has one set up to get around the Memory Charms the wizarding authorities keep putting on her after the incident at the Dursley's. Somehow they never think to check her Walkman for instructions.
A frightening image came to Milo's mind of a thin, pale spider sitting in a large, dark room, surrounded by thousands of silken spider webs, from each of which dangled a major Ministry official like puppets. Milo realized he was badly mixing his metaphors, but, under the circumstances, had other things to worry about.
Miles Gloriosus: Gilderoy Lockhart. Very careful to keep up his "legendary hero" cover.
Min-Maxing: Milo is a little ashamed of himself for not taking full advantage of this, having a Charisma score higher than his Constitution and taking a sub-optimal feat for convenience.
Milo to Hermione: Dumping Charisma is a sign of great wisdom and foresight.
Ironically, that "sub-optimal" feat leaves him minmaxed for the campaign he's actually in instead of the one he thought he'd be in, as without it his magic wouldn't have been sustainable for a week.
Money Multiplier: Using a currency he gets for free (but intends to pay back), Milo shenanigans his way into a way of crafting for something like 1/18000 the proper cost. He's left almost drooling.
Further, it comes down to a matter of scale. The semi-phenomenal, nearly-cosmic powers of magic simply can’t contend with the power of a lot of Muggles working really damn hard all together all at once. It’s like comparing a pressurized water mining tool to all the collective raindrops of a flood.
Mundane Utility: Hannah’s Christmas present is not only absurdly adorable, but can clean suits of armor for her.
Munchkin: Milo not only is one (along with most other members of his home reality), but tries to instill the mindset in his friends. Only Harry is showing any signs of this taking, and even then it's only in pursuit of the ability to protect others, not an end in of itself.
Voldemort himself, when you think about it. Entirely concerned with his own power, he specializes in One-Hit Kill magic without (at first) any known counter, and chooses to make multiple redundant phylanctaries simply because it isn't impossible to do so.
Mysterious Past: Played with. Milo can't remember his backstory ever since he got into Harry's world.
However, with sufficient Character Development (the real kind), he can gradually remember bits he couldn't before.
Nice Job Breaking It, Hero: Milo using Scholar's Touch on the diary of Tom Riddle accidentally copied his soul to his mind. This lead to nearly the entire plot of the second part of the story, with Riddle manipulating everything subtly from his head.
He beats the chess board by pretending to play Ron at chess and instead relaying the Castle's moves to Ron. This teaches Ron the chess board's algorithm, making the chess game he plays for real significantly less dangerous than canon.
When taking Harry to see the Mirror of Erised as in canon, he sabotages Harry by making him believe he needs the stone to save Milo, thereby failing the test that no-one who wanted to use the stone could retrieve it from the mirror.
Finally, he puts on an Amulet of Protection from Evil, driving Voldemort away from him.
Normal Fish in a Tiny Pond: Back home, Milo's nothing special in the grand scheme of things. Here, his potential is equivalent or greater to a legendary artifact that drives the entire first book's plot. Bellatrix, who gets sent to his world is "merely" fairly powerful in the Potterverse. In Milo's world, her abilities to break the turn order rules and cast spells without a daily limit are enough to let her do just about whatever the hell she wants.
Not Cheating Unless You Get Caught: The inability of Potterverse magic to detect Milo’s magic (and vice versa) is used and abused extensively. And not just by the heroes...
Not Quite Human: Status of Milo is unclear, but at the least his brand of magic is wholly distinct from everyone else's.
Not the Intended Use: Milo heavily abuses this in relation to his spells, since the original intention of how to use them doesn't always fit their written descriptions (that is, how they can actually be used).
This comes back to bite him hard in chapter 53, when it is revealed that Milo accidentally copied Tom Riddle's soul into his mind when he used Scholar's Touch on his journal. Milo initially protests how unlikely it is, and how such a function wasn't intended in his spell's use, before realizing that he was in a way going against his principles.
"Love," Milo said flatly. "You-Know-Who was brought down by the Power of Love. Maybe instead of learning magic, we should be putting flowers in our hair and frolicking in the forest like those pointy-eared pansies and singing around campfires. Voldy would be powerless to resist our Flower Power."
"Ha! I'd love to have seen the expression on He-Who-Must-Not-Be-Named's face when a throwaway, poorly thought-out rule from an obscure splatbook that he never even bothered to read blew up in his face."
Player Character: Similar to how he tries to guide young Harry, Dumbledore does his best to have Milo realize that while he was once merely a PC he is now also his own player.
Pragmatic Villainy: Lucius does not want the Dark Lord returned for the simple reason that it is more expedient to achieve pureblood dominance and Mudblood destruction via manipulation of the Ministry’s systemic corruption than more overt and aggressive means.
Powers via Possession: Not voluntary on the possessed’s part, but nevertheless at least one instance is shown granting the technical skill to cast spells that would otherwise be impossible for that person.
Rapid-Fire Comedy: A lot of the fic's humor is based on this. Readers familiar with D&D jokes and references are as likely to be entertained as those who aren't, as a result.
Reality Warper: In addition to standard D&D and HP magic - Milo can at will add details to his backstory
"Uncle Reginald!" Milo said, moving to the next guard in line. "Why, you taught me my first cantrip! And Second Cousin Reggie! Remember all those long nights in the woods hunting, er, huntable animals? And, why, if it isn't Adopted Cousin Regan! What unspecified good times we had!" Pretty soon, they all had their weapons lowered, and were milling about in confusion.
"What did you do?" Relkin asked in a hushed voice.
"I remembered each and every one of them as a treasured friend or relative from my backstory," Milo said quietly. "One who would never, ever raise a hand against me or impede the cause of Justice or the furthering of Good. And who gets +2 and a reroll against magical orders against their nature."
Resting Recovery: Milo's health works on D&D rules, which is quite disturbing to Madam Pomfrey.
Ridiculously Cute Critter: Hannah’s Christmas present is literally the cutest form of her favorite animal that her mind can conceive.
RPG Mechanics Verse: Milo’s home reality. To the point that he has trouble understanding he’s no longer in one.
Though in all fairness to him, he does still personally follow RPG rules, and has no way of knowing what rules others follow except through observation, which is colored by his personal bias. Refer to his deduction that Hogwarts students must spend (eight minus their intelligence bonus) hours sitting in armchairs and talking about the weather.
Rules Lawyer: Being the munchkin he is, nobody reading this should be surprised Milo is this.
Running Gag: "Hufflepuff — Not that that's anything to be ashamed of." and "Everyone knows that"
Also Milo saying he shouldn't have dumped Constitution at Character Creation.
Also the fact that "irregardless" is grammatically incorrect.
Aberforth thinking that people are talking about him when someone mentions Dumbledore, only to get disappointed when they clarify that they were talking about the other Dumbledore.
Schrödinger's Gun: One reason Milo prefers to leave parts of his backstory undefined is that it lets him pull this when necessary. Such as in Chapter 53, in which he considers "remembering" that his mother made the same kind of Heroic Sacrifice that Harry's did, but ultimately decides against it.
Shout-Out: The author subscribes to the idea that, since the people of Milo’s world don’t really have pop-culture, they make pop-culture references without control or knowledge why.
Hermione decapitating the Basilisk with the Sword of Gryffindor is clear reference to Jabberwocky, complete with a "Snickersnack!".
While the two Muggle police officers are on stake out pretending to be bird watching, Travis mentions he's part of the BBC (British Birdwatching Community). Fiona quips that next he'll tell her he's the voice of the Daleks, and asks him to put in a good word for her with Tom Baker next time he sees him.
"Unless, of course, you aren't human, and are some form of hitherto-undiscovered magical creature, in which case you'll be staked, beheaded, buried upside-down in sanctified concrete for a year and a day; then dug up, salted, shot with thirteen silver bullets, cremated, and Disapparated into the sun."
Title Drop: In downplayed, subtle ways. A 'natural twenty' is an attack that is guaranteed to hit, and a possible Critical Hit. Two of these notably happen throughout the first part: First, when Milo throws a dagger at a possessed Hannah, nearly killing her. The second is similarly when Milo throws a dagger at Quirrel in that part's climax, but it fails due to Voldemort taking over and simply stopping it with his magic.
To Be a Master: Milo is something of a deconstruction, showing the ultimately empty life devoting oneself to mastery alone leads to. Much of his Character Development is aimed towards giving him something, anything else, to desire out of life besides being a great Wizard.
Trapped in Another World: Milo (and Bellatrix, who took his place). Although Milo’s changing attitude and our glimpse into the witch’s glee may suggest neither really feel all that trapped.
True Meaning of Christmas: Harry has to put his foot down to stop Milo from going on an adventure for this as soon as the possibility is presented to him and insists they all just have a normal Christmas together. Unfortunately, due to factors beyond his control, Milo winds up being forced to do it anyways with Hannah.
Supremely Evil Fell Lord Thamior the Thaumaturge (try putting that on a business card).
Twin Switch: Fred and George try the varient of having one twin pretend to be the other to provide an alibi. Milo either doesn't care that the name he uses is being corrected, or isn't fooled for an instant and dismisses the correction out of hand. It isn't clear which.
Uncle Pennybags: Harry is slowly becoming this, even more so than in canon, thanks to Milo's reliance on Harry's inheritance to fund his spell research, Item Crafting, and spell foci.
"Well, it takes an hour," Milo said, "and it's not guaranteed to work. Also, I need a big expensive mirror."
"How expensive?" Harry asked.
"A thousand gold pieces—or, via salt, thirty-seven galleons, seven sickles, and eighteen knuts."
Harry made a dismissive noise and shrugged. "I thought this was supposed to be a problem."
Unreveal: Whenever Milo pulls off a feat of Munchkinry that his author couldn't match, his methods are rather obtusely, obviously, and humorously left offscreen. This includes how Milo managed to become a Wizard while still a child, how he passed his Transfiguration first year with full marks and no talent, and how he managed to get a certain feat so early.
Vancian Magic: Milo has off and on again feelings of inadequacies brought on by everyone else’s ability to completely bypass the hard limitations of his relationship with this trope, especially the fact he can "run out" of magic.
Milo is nearly expelled when an enemy arranges to exploit this and make it appear as if he has no magic at all.
In chapter 53, Milo wonders about the morality of retconning his backstory to include tragic events. Nothing in his backstory actually exists until he defines it, so if he adds a tragedy to his backstory, it's as though he caused it himself.
Weird Currency: The idea of using anything but precious metals or barter goods is incomprehensible to Ron and Milo until they realize that, without any form of magic, Muggles have (relatively) no way of counterfeiting.
Ron: Whoa. That's mindblowing. They can use anything as money, then. I should write my dad about this.
The Worf Effect: Milo defeats (often handily) multiple powerful wizards and monsters on numerous occasions. However, at the beginning of the second book, some Muggle police officers manage to best him. Considering that the British police don't readily carry firearms, they weren't particularly powerful or dangerous compared to other enemies Milo has faced.
When something really, really, really wyrd happens, and hear ye me I do mean REALLY wyrd, and lo, it hath never happened before, and neither sir nor gentle lady knoweth what to do, let the goddamned Department of Mysteries handle it, y'hear? And forsooth, maketh sure there are at least a half-dozen Aurors around, if ye know what be good for ye.
—1634 Statute on Inexplicable Phenomena of a Magical Nature, Section Thirty-Two-Point-One-Four-One-Alpha