Horace Slughorn

Professor (Whenever a nontoken creature enters the
battlefield uncer your control with a lower toughness or
power than this creature, put a +1/+1 counter on it)
At the beginning of your upkeep choose one:
• Put 2 +1/+1 counters on target creature
• Return an instant or sorcery from your
graveyard to your hand
• Put 2 -1/-1 counters on target creature.