Bene Gesserit's Test

Target a creature. Its controller reveals cards
from the top of their library until they reveal
a land. Put all cards revealed this way on the bottom of the library in any order. For each nonland card revealed, put that many -1/-1 counters on that creature. If the creature
doesn't die from this, remove all -1/-1 counters from it and put that many +1/+1 counters on it instead.