I would also include Foundry Inspector as an honourable mention, though it just loses out due to costing 1 more mana
It wouldnt even need to be a tribal deck for Cavern of Souls to be valuable
You might also consider running Horn of Gondor to increase your human creature count, or Karvanista, Loyal Lupari to spread out +1/+1 counters on attacks, or even Cloaked Cadet for some extra card draw
First, theres the Clone type, a card that can be a functional copy of another creature on the battlefield, with variation on whether it's yours, theirs, or either
Creature - Bird Color tag templates(None) Guardian Gladewalker Changeling (This card is every creature type.) When this creature enters, put a +1/+1 counter on target creature
For one white mana, youre technically casting a 1/1 lifelink creature