Thief of Sanity copy effect

wereotter

When Thief of Sanity hits my opponent, rather than give me a copy of my opponent's top card to my hand with half its mana, it puts that copy on top of my library with no mana.

Tremayne

That explains why this card is so meh. Another card on the thrash, which may have potential if fixed.

biopower

I just tested it and it works fine. I'm pretty sure that you're running into the Fblthp problem (see https://forums.d3go.com/discussion/comment/890040 and https://forums.d3go.com/discussion/comment/890729). Fblthp breaks fetch AND copy abilities, even if it's in your opponent's deck.