Woodland Troll

Wither (This deals damage to creatures in the form
of -1/-1 counters.)
When Woodland Troll enters the battlefield, you
may search your library for a Troll card, if you
do, reveal it. Shuffle your library, then put the
card on top of it.
{r/g}: Regenerate Woodland Troll. (The next time
this creature would be destroyed this turn, it isn't.
Instead tap it, remove all damage from it, and remove
it from combat.)