You should really make avatars appear in the purges, especially when you get those from Jhebbal Sag, he should really appear in the flesh during the purge.
Furthermore, when there is a Lemurian purge, Hanuman should really make an appearance. You already got the gorillas so you only need to make a really big and powerful version of them and cal it the Avatar of Hanuman
In addition to this, Jhebbal Sag should also appear during purges from the Dogs of the Desert.
When there are purges by the Heirs of the North or by the Lost Tribe of Cimmerian, you should add the avatar of Ymir to the fray.
Set should appear when the Relic Hunters do a purge.
To give the defenders a chance to prevent the appearance of an avatar of the gods, make it so that the purge has an archpriest summon the avatarof their god but it takes some time and if the defenders kill or capture the archpriest before the summoning ritual is complete, then the avatar won’t be summoned.