The Fallen, formerly known as Megatronus Prime, was the Founder and True Leader of the Decepticons, and the master of Megatron who served as the overarching antagonist of the Transformers franchise. After his ambitions grew to a point of irreversible evil, the other Dynasty of Primes turn their back on him and hid the Matrix of Leadership from his reach, eventually hiding it on the once barren Earth.

Evil, leader of the Decepticons, a Prime

Megatron can transform into a Cybertronian jet. His right arm can turn into a fusion cannon, and his left arm can transform into a flail mace. 

The power-hungry, leader of the Decepticons

Turtle is a quiet, not wanting to be noticed kind of Seawing. He is outwardly friendly and is a prince. His sisters are Tsunami, Anemone, and Auklet. His brothers Octopus and Cerulean, plus another 19. His mother is queen Coral. He cannot inherit the throne to the Seawings because only queens can exist. Turtle and his friends: Moon, Qibli, Kinkajou, and Winter, stopped a giant two-thousand-year-old animus Nightwing with mindreading and prophecy powers from taking over the world. 

A quiet, out of the way Seawing.

The Big One is dark brown, with black stripes going down her back, she has yellow eyes, and sharp eyes that "When she looks at you, you can see she's working things out."
—Robert Muldoon

Highly aggressive Velociraptor.

It has 6 limbs consisting of a pair of hind legs and 4 arms: a pair of large pillar-like ones with clawed hands capable of grabbing prey at the front, and a pair of small ones resembling an elongated version of the arms that regular Tyrannosauruses have located closer to the body between the other limb pairs. It moves on its larger arms and hind legs, giving it a great ape-like build as well as a quadrupedal gait similar to dinocephalians like Moschops and pareiasaurs like Scutosaurus. 

A massive mutant dinosaur aka the D. Rex.

Like its packmates, Ghost is extremely violent and reckless but also quick on its feet, meaning it is perfect for tracking down and killing targets. It is most likely that Ghost is the leader of the pack. Has external ear drums, like a lizard.

Ghost is extremely violent and reckless.

An unstable hybrid dinosaur, that sees through thermal vision, has poisonous quills on it's tail and head from the scorpion fish DNA it had, experiences large mood swings, usually involving killing things. Also called E750. Extremely aggressive will attack on sight, most of the time.

An unstable hybrid dinosaur. Also called E750.

Blue has gemlike azure, bright morpho butterfly blue, and lavender-purple scales, with purple scales on his back, quiet lavender scales on his arms, azure talons, and a purple snout. His body glints with purple and aquamarine like buried jewels, and his wings shimmer purple and bright cerulean blue, like sapphires and violets tumbled together. He has glowing embers under his wrist scales due to being a flamesilk. He is fairly small, but larger than Cricket.

A small male flamesilk SilkWing

While in costume, Shiro wears white robes and a mask over his face, all made from anti-sensei fibers. Additionally, the back of his torso is adorned with a Bohr model of the hydrogen atom. Shiro also utilizes a voice modifier to further hide his identity from Koro sensei. When unmasked, Yanagisawa has short, wavy dark green hair and pale teal eyes, along with fair skin. As a result of his confrontation with Koro sensei two years prior to the events of the story, a prosthetic eye is his left eye.

He is a mysterious scientist.

Velkhana is a traditional dragon with the slim, upright body structure of Elder Dragons like Kushala Daora. Its scales and shell are a unique crystalline blue. Its head has a tiara-like crown of small horns. It summons ice to cover its wings, limbs, and tail. Its thin, lance-like tail is highly flexible and can jab at enemies. 

A female ice Elder Dragon

Zoe is a tan robot who floats around via repulser lifts. She has to large yellow eyes and a yellow sensory antenna on her head. She has a blue right arm and many gadgets that aid her in her smuggling job with her captain.

Known as Zoe, sassy independent, tries to be funny

The monster is a 240-300 foot high quadruped with long tri-fork finned tail. The uppermost double-jointed limb pair is longer than the other two, ending in a multi-fingered hand which can bend backward so that the creature can walk on its fingers. The double-jointed, squat legs are powerful enough to support the creature’s mass, and yet still allow it to move relatively quickly for an organism of its size. Each of its feet is 30-40 feet in length, roughly the size of a city transit bus.

Cloverfield is an unknown aquatic creature

After the Athena-1 satellite exploded in Earth's atmosphere, one of the capsules containing Energyne's experimental "Project Rampage" pathogen crashed into Everglades National Park in Florida. The capsule was promptly swallowed whole by a crocodile swimming in the waters where it landed. The pathogen took effect, editing the crocodile's genome with weaponized DNA that had been developed aboard the Athena-1.

A large, mutated and aggressive crocodile

She is a kaiju named Otachi.
Otachi is maybe 270 long. (Not really specified and I was also unable to find her height)
Otachi weighs 2,690 tons

She is a dangerous, large, and pregnant kaiju.

Optimus Prime is a master combatant; he is shown to have a powerful and aggressive fighting style, wielding deadly Energon blades or powerful Ion blasters. He also has a habit of targeting his enemies' heads. For example, he decapitated Bonecrusher with an energon sword, he killed Demolisher by blasting him through the head with an Ion blaster, he killed Grindor by ripping his head off a pair of hooks, he killed Shockwave by ripping out his eye and throat.

Optimus Prime is the leader of the Autobots

She also dislikes arguing.
Cyprus is a green LeafWing with blue and golden scales dotted around on her body, as well as some dark green. She likes drawing and was a part of the more peaceful part of the LeafWing tribe before Wasp’s defeat.
She’s calm and likes joking and describing her art. She’s also very friendly to everyone possible. She is also a good story writer. (Also an irl YouTuber).

Likes avocados,cats,strawberries dislikes bananas

He is a brown dog-horse. He’s friends with a small wizard named Nigel and has a British accent. He has a flat-ish tone, though emotional does come through. He is sensible and fairly smart.

A brown dog-horse who has a flat-ish voice

Sandowrms have an array of crystalline teeth which are used primarily for rasping rocks and sand. During his first close encounter with a sandworm in Dune, Paul notes, "Its mouth was some eighty meters in diameter ... crystal teeth with the curved shape of crysknives glinting around the rim." They do not have tongues, and they have a giant hole for a mouth, that's able to contract to close. The damn thing doesn't have eyes. It cannot open and close its mouth very fast.

A giant 1300 foot long worm from Arrakis

Burn was an adult female SandWing who was introduced in The Dragonet Prophecy. Among Blaze and Blister, Burn was the most brutal princess during the War of SandWing Succession, and was widely feared in Pyrrhia. She was allied with the SkyWings and later, the MudWings after the assassination of Commander Tempest. She resided in the SandWing stronghold during the war.

The rightful queen of the Sandwings

Nigel speaks in gibberish English that still is recognizable as English, he has yellow skin and dark blue robes along with a cone shaped hat. He is British, though because of his gibberish way of speaking, the accent is not very prominent. He has magical powers to make things grow or shrink. His best friend is named Marmalade who is a dog/horse. He is tiny and likes candy, snacks and TV. He’s also friends with a pink blob named Patricia who makes baked goods and is a criminal. He’s childish.

Yellow little wizard with blue robes and a hat

Born in 2012, the Indominus rex escapes in 2015. The Indominus rex is 20 feet tall and 50 feet long at full growth, and hunts for sport. She is made up of multiple dinosaurs, including: T rex, Velociraptor, Therizinosaurus, Gigantosaurus, Carnotaurus, Rugops, and other animals. She is able to communicate with raptors, and is seen attempting to communicate to the T rex. She is also able to camouflage into her environment. She is also fairly glutenous.

A very aggressive, psychopathic hybrid

Aleksandar, Prince of Hohenberg, usually known simply as Alek, is one of the main characters and protagonists of the Leviathan series. He is a 16-year-old Austrian boy. Alek is the son of Archduke Franz Ferdinand and Sophie Chotek, Princess of Hohenberg. Because his parents' marriage was morganatic, Alek is not allowed to inherit the throne of the Austro-Hungarian Empire. After his parents are assassinated, Alek goes into hiding with several men who worked for his father.