Conversation so far:
Was Comet good or bad?
Comet's appearance was unclear.
What superhero was he with ?
Supergirl.
What powers did he have?
could shape-shift between her human and super-powered forms.
What did Comet look like?
surrounded by an aura of cold.
Who was Comet?
hero with flight and cold-generation powers.
Was he/she a male?
his.

Question: What is his back story of how he came to be?
Self-contained rewrite: What is Comet's back story of how he came to be?