Aerie Diver is a very niche tool in this faction's arsenal and is intended for two specific uses:
The first is to finish up units without the need to spend an attack. Skyspear Avians are a faction that has no way to break the 3 attack limit rule, and that also focuses more on expensive units. Yet because of their high mobility they often have multiple contact points. Having to spend an attack to finish up a 1 life unit is very annoying and that's where Aerie Divers come to fill the gap.
The second use is to support Ava offensives. Skyspear Avians are a faction that use their 3 movements a lot, bringing reinforcements to the front lines and repositioning them is quite difficult sometimes. Aerie Divers help with that by providing units that can be summoned right where you need a unit to be without needing to spend movements to get it there.
Outside of those 2 uses though, Aerie Divers are very underwhelming, as a 2/2 for 1 magic cost is overpriced.