This card is kinda funny.
You play a warlock orb, the opponent tries to steal it, you stop it with the orb and then use it's new ability to steal from the opponent. You just countered a spell and stole a permanent. Imagine if it's another warlock orb!
It's a little overpowered as it is, I'd make it a counter to abilities instead.
I'm not sure how devour would work through.