Timid Giant

Undersell (You may pay {x} less to cast this creature. If you do, it enters the battlefield with X -1/-1 counters. If this creature becomes the target of a spell or ability, remove all counters from it.)
This creature cannot attack or block if it has no -1/-1 counters on it.
{t}, Remove a -1/-1 counter from this card: Regenerate it.