Need a totally awesome magical beast to make your show that much more awesome? Why make one up when mythology's done it for you? The Behemoth, the Leviathan, maybe a dragon or two. In works involving the afterlife, you can even expect Cerberus to make an appearance.

But wait...in their original forms, these guys weren't quite awesome enough! We need to give him NEW powers so he presents a real threat to our heroes (or our villains). Behold the power of creative license! Time for a MythologyUpgrade!

Cerberus not cool enough? Let's give him a [[BishonenLine human form!]] Raging dragons not doing it for you? Let's make them [[DungeonsAndDragons superintelligent and magic-resistant!]] Leviathan not dangerous enough in the water? Let's make him [[DevilMayCry FLY!]]

Note that the Mythology Upgrade refers specifically to an already established creature of legend who gets entirely new powers, not one that just mysteriously got more powerful. Compare PublicDomainArtifact.
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!!Examples:
* Franchise/ShinMegamiTensei and all its incarnations, with various demons and mythological figures.
* Dragons are perhaps the greatest recipients of this trope. Besides their fire breath and animal ferocity, most myths didn't give them many additional powers. [[NewerThanTheyThink Modern sources]], however, almost always depict dragons as gigantic beings of incredible physical and magical strength. ''TabletopGame/DungeonsAndDragons'' is one of the worst offenders. See OurDragonsAreDifferent for the various permutations.
** Earlier than Dungeons and Dragons, Creator/JRRTolkien's dragons were huge, highly intelligent, possessed magical powers (particularly mind-bending magic), and were quite possibly incarnate minor deities, if evil ones. WordOfGod admitted a certain fondness for this particular creature, so he used them sparingly but when he wanted to go for grand effect.
** And the magic powers and wisdom come from the Asian dragons that are essentially minor gods or elemental powers.
* ''FinalFantasy'' pretty much owns this trope, since several of its enemies and almost all of its summons are taken from mythology, and then powered them UpToEleven. List examples below:
** Bahamut, who makes an appearance in almost every game, is the King and/or God of all dragons. In his FFX incarnation, he has a giant ring on his back which charges with energy to unleash his [[LimitBreak Overdrive,]] which is basically a [[FrickinLaserBeams giant blue laser.]]
** Shiva, who goes from six-armed hermaphroditic deity to surprisingly well-endowed and ''definitely'' female ice goddess.
*** That may be a coincidence, as her name is evidently supposed to be Shiver but given Japanese language barriers, is rendered as Shiva.
** Leviathan in Final Fantasy VIII indeed ''does'' fly.
** Adrammelech, a pagan sun god who [[RuleOfCool for some reason]] has electric powers and looks like a dragon.
*** It looks more like a flying goat
*** {{Castlevania}}: Circle of the Moon made it a giant, eyeball controlling, ooze gagging goat thing that [[ThatOneBoss pissed off players]].
** Cu Chulainn, Ixion, and many others bear [[InNameOnly almost no resemblance to their mythological counterparts]].
** Both Bahamut and Shiva's cases are really examples for Mythology ''Down''grade since both are way more powerful in the original myths. Bahamut is a whale-like EldritchAbomination that is larger than the world (and the world is so small compared to Bahamut, since it only floating in a small crack on a bull's head, said bull is standing on Bahamut's back). While Shiva can burn the world simply by opening his third eye.
*** And while we're at it, said bull shows up in FinalFantasyVII as a tri-elemental summon. Still a bit of a downgrade, but hey, random elemental powers!
* It should be noted that in the myth Bahamut isn't exactly carrying the world, though it is the most common interpretation and perhaps what the original myth intended, the exact words say that it was carrying: "all of god's creation".[[Creator.JorgeLuisBorges Some authors]] have played with this and stated that what it is actually holding is the [[BiggerIsBetter universe]]. This is actually a an [[IncrediblyLamePun enormous]] literature upgrade.
* ''DevilMayCry 3'' had the legendary Leviathan as an enormous flying creature with a demonic immune system, which Dante has to fight through to kill the creature from the inside out.
** Not to mention giving Cerberus some wicked ice powers. Or Beowulf turning from a human BadassNormal to a [[LightIsNotGood light]]-flinging demon. Or Geryon having time-control powers. Although, Cerberus's ice makeover does work nicely as a homage to the coldness of hell in Dante's Inferno. Complete with him guarding the gateway to hell (temen ni gru).
* ''VideoGame/{{Touhou}}'' has most of its LoadsAndLoadsOfCharacters taken from Japanese mythology. [[MoeAnthropomorphism They all look like little girls]] and are each capable of [[BulletHell Curtain Fire]], an ability notably absent in their source material.
* In ''SluggyFreelance'' a succubus is a bus that sucks you up. [[http://sluggy.com/comics/archives/daily/050822 Seriously.]]
* Cerberus deserves a special mention in any appearance he makes, since the original creature, depending on which myth you're going by, had snakes growing from his back and was formed by/had skin made of the ''squirming souls of the dead.'' Which practically makes many of his appearances a Mythology ''Down''grade.
** It should also be noted that Cerberus originally only had one head, not the three he is famous for having. That didn't come until the Romans got to him (making this an OlderThanTheyThink trope in and of itself). He was also often portrayed as an average sized dog, rather than the gigantic monstrous beast many relate him to. This is of course assuming that Hades is an average sized man, which is difficult to tell with gods...
* ''Dante's Inferno: An Animated Epic'' -- The animated short had Cerberus, who was already pretty frightening as a three headed fire breathing dog, reinvisioned as a giant colon like monster with many mouths and residing as a guardian in the third circle of Hell, Gluttony. The gluttonous souls swallowed by Cerberus are forever denied the pleasures they overindulged in while alive. Cerberus's stomach is also the realm that Dante had to cross to enter the next circle of Hell.
* An arc of the ''Anime/YuGiOh'' anime gave the Leviathan strange powers related to souls and [[SeriousBusiness children's card games]]. It could apparently make people immortal and/or "awaken the darkness in their hearts", and was said to be responsible for the fall of {{Atlantis}}.
* TabletopGame/{{Scion}} upgrades various mythological beings with modern elements. Examples include Centaurs as half-human and half-Harley-Davidson motorcycles, Scylla having machine replacements for its monster heads, and Surtr's main fortress in Muspelheim being able to transform into a HumongousMecha.
* WhiteWolf also generally did this with their ''Werewolf'' game lines. It's not enough that they're shapeshifting killing machines -- to fit roughly in with the themes of works such as ''The Howling'' and ''Wolfen'', werewolves also have ties to nature that give them access to the SpiritWorld and a special relationship with its denizens. Whether this relationship is "[[TabletopGame/WerewolfTheApocalypse stalwart defenders]]" or "[[TabletopGame/WerewolfTheForsaken border police]]" depends on the gameline.
* This isn't a ''VideoGame/NetHack''-only feature but the lore change of [[http://en.wikipedia.org/wiki/Medusa Gorgon Medusa]] is probably the most famous mythological ''downgrade'' of any mythological monster. Originally, Perseus faced the Gorgon by looking at her reflection in his mirrored shield and cutting her head off. Over time, a more pacifist approach was adopted that Medusa could stone herself by looking at her own reflection.
* Arachne is simply a progenitor of all spiders in ClassicalMythology. If there are monsters with that name in modern works, they are always half-spider half-woman beings with human size, if not larger.
* Many of the monsters from ''VideoGame/WillRock'' have extra powers: the Minotaurs can [[AsteroidsMonster split in two lesser ones]] when slain, the Harpies shoot fireballs, Cyclops have goat legs and can eat and spit hot stone pellets and Orthuses can spit fire and acid from their heads.
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