Atla Palani, Nest Tender | Mirror Entity | Purity

Cards

Increase Atla's toughness by at least one.
Activate
Mirror Entity an arbitrarily large number of times by paying a total of ({0} magic symbol) .
Resolve the first
Mirror Entity ability, causing all creatures you control to have base power and toughness 0/0 and gain all creature types until end of turn.
All creatures you control except Atla die as a state-based action due to having zero toughness.
If
Purity died this way, it triggers, shuffling itself into your library.
Atla triggers once for each creature that died.
Resolve the first Atla trigger, revealing cards from the top of your library until you reveal a creature card, then putting the creature card onto the battlefield and all other revealed cards on the bottom of your library.
Repeat step 7 for each remaining Atla trigger.
Repeat from step 3 for each remaining
Mirror Entity ability.