Tiamat is the most insecure little thing ever. She has both Hero and Dark genes so she's conflicted about her appearance, since the normally monstery-looking Dark Chao don't bat an eye at what some might consider freakish deformities. She's self-conscious about her very long jesters and flipper feet. She often ties her long hair up around her jesters to hide them and make them look like twintails. She's also a poor swimmer, so she has very small arm frills and hasn't developed gills like a lot of the swimming types. She prefers to just relax quietly in the water.
So far Tiamat's only defining characteristic is her stupid sweet moe insecurity and timidity so bear with me as I develop her some more. e_ e;