Zero was born with a rare disease that makes his immune system super weak. One of the things it caused was that he never grew a coat or tail. He grew up living in a clean room, but he eventually had a spell cast on him that protects him from sickness. It has to be refreshed every once in a while and near the end of the spell's life, he starts getting sick really often until he just has to either get the spell cast again or start quarantining himself.
I don't know if I'll ever use him again or not but if so, he'll probably get a redesign.
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