They are their own sacrifice outlets, which can cut out the middleman in a Naya recursion deck
Incorporate your deck with creatures that have ETB effects like token creation, card draw, or destruction of permanents for added value
This card is simply insane in every deck that wants its permanents to hit and leave the battlefield over and over again
If the mana generated with Arena of Glory's last ability is spent on two different creature spells, each of those spells (and resulting creatures) will gain haste until end of turn
Nahiri, the Unforgiving is a cheapo walker that can loot, and grab temporary creatures and equipment out of the yard
Treat phased-out permanents and anything attached to them as though they don't exist until their controller's next turn.) To proliferate, you can choose any permanent that has a counter, including ones controlled by opponents