Ambitions of the Stag

Menace

Whenever Ayara’s Oathsworn deals combat
damage to a player, if it has fewer than four
+1/+1 counters on it, put a +1/+1 counter on it.
Then if it has exactly four +1/+1 counters on it,
search your library for a card, put it into your
hand, then shuffle.

(Ayara's Oathsworn)