This spell can't be countered.
Flying, vigilance, trample
Players can't cast spells from anywhere other than their hands.
Spells your opponents cast that cost less than five mana to cast and target you and/or spells or permanents you control cost five mana to cast.

Flying
Amity — Whenever you attack with Warden of Soul and exactly one other creature, search your library for a legendary or Dragon card, reveal it, put it into your hand, then shuffle.