If Only He Knew He Knew

Not really, 'magic clone' is about it.

Though hunter describes himself as "a clone". When Gus sees the statues of Philip and Caleb he recognizes Caleb/Hunter and apparently already knows what a grimwalker is (as does everyone else when the secret is outed).

There are some details shown in background art. The one I can remember is that they don't have a heart, they have a galderstone instead.