The Eldritch Abomination as an animal.
"This was no chicken, it was evil manifest."It's big. It's powerful. It's nasty. And it's not humanoid, but familiar all the same. This trope is for Eldritch Abominations that either naturally resemble (somewhat) ordinary animals, or else possess Animorphism and spend a good deal of time in the animal form.
Kahlan Amnell, The Sword of Truth: Soul of the Fire
Anime and Manga
- The Tailed Beasts from Naruto fit easily, save the Ten-Tailed Beast, which is a more traditional Eldritch Abomination.
- Kyubey from Puella Magi Madoka Magica might qualify.
- From Berserk: The Beast, possibly the sentient incarnation of Gut's hatred and rage (and boy does he have a lot of either) usually takes the form of a large canine with lightning-bolt eyes. The Berserker's armor, which previously had a Skull For A Helmet, is in the shape of a snarling wolf's head now that he wears it.
- Gyo has zombie fish with metal spider-like legs.
- In The Thing the monster spends most of its time as an Alaskan pack dog. You catch a glimpse of what it really is, before it proceeds to eat all the other dogs.
- Mogget and the Disreputable Dog from the Old Kingdom trilogy. Respectively, Yrael and Kibeth the Bright Shiners.
- Besides those, a few other Free Magic creatures have animal-like forms. The thing at High Bridge is basically a boar made of fire.
- Clark Ashton Smith's "The Seven Geases". The Cthulhu Mythos deity Atlach-Nacha resembles a huge, hairy and hideous black spider.
- From Sword of Truth, the Chimes of Death, for whatever reason, take the forms of chickens.
- Ungoliant is equal parts Giant Spider, Mother of a Thousand Young and Eldritch Abomination. Her daughter Shelob may also qualify.
- Speaking of spiders, Its second-to-final form is one.
- Norse Mythology features Fenrir, Hresvelgr, Ratatöskr, and Nidhoggr.
- From Judeo-Christian myth comes the Ziz and the Leviathan
- Shadowrun has a lot of these in the form of magical beings like the totem Spider which plots world domination and manifests as a huge spider in astral space, and the Sega Genesis game has Thorn, a dog or coyote-like malevolent spirit.
- RuneQuest. In the Glorantha campaign setting one major empire has an enslaved Chaos god/demon/thingy called the Crimson Bat, which looks something like a giant bat.
- In The Elder Scrolls series, several Daedric Princes have animal forms. In particular, Hircine appears in the form of a large white stag, and Clavicus Vile's conscience takes the form of a literal Morality Pet: a dog named Barbas.
- Dragon Age: Origins features Witherfang, the giant wolf commanding a tribe of werewolves, who is presented to you as one of these at first. It turns out, however, that it is merely a wolf body possessed by the spirit of the forest it lives in--and one of the most human characters in the entire game.
- The Beast in chapter one of The Witcher is a huge dog-shaped manifestation of the collective sins of an entire village, materialized to haunt and terrorize them.
- If you think about it, Amaterasu is one of these as well, being the goddess of the sun in the form of a wolf.
- A lot of the monsters from Silent Hill resemble animals. Dogs, cats, bird-bat things, roaches, and a crocodile have all been demonstrated.
- In The Elder Scrolls V: Skyrim, the dragons are more akin to angels/demons, and Alduin himself is a god.
- Spiders must be popular. Asura's Wrath gives us the Golden Spider, who's actually Chakravartin in disguise.
- From the same game, the Gohma also qualify.
- The Liir of Sword of the Stars resemble dolphins or whales with a number of features from other sea creatures (fur, tentacles, negligible senescence...) and Psychic Powers, but most of them are simply Starfish Aliens. The Suul'ka, on the other hand are bigger than most starships, feed on the life-forces of planets, are summoned from the black depths of space where they slumber by mass sacrifices, and have a method of "teaching" their followers via direct telepathic contact that is almost always fatal for the follower.
- The Final Boss of The Legend of Zelda: Phantom Hourglass is quite obviously based on the giant squid. Makes sense, since its greatest enemy is a whale god, who may or may not also qualify.
- Questionable Content has Randy the Bandicoot. He is eternal.
- Becquerel and the G-Cat from ''Homestuck are First Guardians, giving them Reality Warper powers.
- Two Masters : The Master of Heaven, Yehveh. Its a Shining Big, Badass Bird of Prey, and a god In-Universe.  It also takes the form of a lady when... moving... 
- In Gunnerkrigg Court Coyote's true form when viewed in the ether looks more like a mass of brightly colored tentacles with teeth and eyes than his usual abstract painting of a canid form.
- There Will Be Brawl: The final form of the not-of-this-earth Mr. Game and Watch is an octopus.
- The SCP Foundation has contained a number of these, some of the most notable being SCP-1055, SCP-682, SCP-334 and SCP-953.
- Almost everything with the "animal" tag qualifies as one of these.
- My Little Pony: Friendship Is Magic features a slew of these as villains. Nightmare Moon, Discord, the Windigoes, Queen Chrysalis and the Changelings.
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