Plagueling

He actually has a soft gooey center, but grew up in a terrible environment where everyone thought he would be nothing, because no one where he was raised grew up to do good things
He became bitter and though became a successful investigator, he became a product of his environment and lets the bitter cruelty rule him
It's a way to distance himself and protect a heart that is underdeveloped when it comes to trust and is actually quite fragile

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It was too much. He couldn’t keep it under control anymore. His anxiety came out, like it always did, in the form of anger. The dark-colored Mirror turned away from the brighter pair, paws stomping as his wings curled in and mantled over his shoulders.

‘Why do you always push everyone away?’ Seed's confused face and Delight's soft question, though obviously not meant to be heard, cut through Plagueling's angry and anxious storming off fuming.

He didn’t know. But he hated it.