maybe it could still cost B... but like you said you could pay X and sacrifice it to make them dump their hand..
maybe it could keep getting counters when your opponent does something good for themselves...
something like
when an opponent does X, put a counter on this..
B, remove a counter from this: target opponent discards a card
that way it's more of the opponent's restraint...
and they won't walk face first into it...
it would have to be an anti black ability though... possibly when an opponent gains life... that way they could simply avoid doing so.. but it would be similar to a really weak forsaken wastes..
the waiting 2 turns thing to kill a hand is cool, but i didnt even think about how horribly it would rip through a counter deck...
if i made the only trigger gaining life, then it's strictly a sideboard card.. but i think if i added 2 triggers it would be playable..
couldnt be whenever an opponent casts a spell that deals direct damage
couldnt be whenever an opponent casts a spell that draws them a card
it would have to be something white/green based...
white gains life... whats exclusive that green does, spell wise?
hmmm..
here's maybe what it would look like..