There's an advancement trigger for summoning an entity, so it would be useful if summoning an entity with Abyssalcraft fired it. Would just mean adding

for (EntityPlayerMP entityplayermp : world.getEntitiesWithinAABB(EntityPlayerMP.class, entity.getEntityBoundingBox().grow(range)))
{
CriteriaTriggers.SUMMONED_ENTITY.trigger(entityplayermp, entity);
}

right before/after the entity is added to the world with world.spawnEntity(entity);