Creature — Human Knight
2 / 2
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.
If Ayara's Oathsworn isn't on the battlefield as its ability tries to resolve, you won't search for a card, even if Ayara's Oathsworn had three +1/+1 counters on it before if left the battlefield, because it won't be around to have the fourth +1/+1 counter put on it.