Perfect Form: In this form, Thanatos looks like a blue-coloured seraph angel.

It has a golden plate on the back of their necks running down its back. It has two large wings that protude from its lower back. These protrusions each have a spike followed by three spearheads running along each of them. It has two protrudents on its back - one on each side of the back. Its shoulders look like large balls connected to the arms and the body. It has long, golden veins that run from its shoulder to the back of the hands. It has long, lean, but very strong arms and wears two golden bracelets on each arm and several golden nails nailed into each forearm. It always has its mouth open and look as if it's grinning. It has white eyes with black circles around them. Adult Form: In this form, Thanatos looks like a huge humanoid dragon.

This form closely resembles its Adult Form. It also has two wings coming out from the lower part of its back. It has two crests, one on its forehead and the the other one above its neck. All Its eyes are always closed and its mouth is jagged like sharp teeth. It has dark-yellow, upright scales running along the back of its longish neck. Its forearms are protected with blue, metallic forearms protectors, and has blue metallic bracelets. All three of these spearheads are connected by a metallic brace. It has six metallic, spearhead-like protrusions coming out of its back, three running down a vertical line on each side of the back.

Juvenile Form: Here Thanatos looks like a seahorse that stands at about the same height as Sieg and has a very lean physique.

In this form, Thanatos is the smallest legion in the game. The egg also has a pair of wings sticking out on each side (kinda like a tadpole with wings).

Baby Form: Thanatos looks like a white egg, about the size of Sieg's head, with a flaming tail.

Thanatos' appearance changes drastically as it Force level increases.

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