Tienaela, Apocalyptic Angel

Flying, haste, demonslayer
Unseal 7 (If this card would be exiled or put into a graveyard, instead exile it with seven seal counters
on it.)
Whenever a creature dies, remove a seal counter
from Tienaela. When the last is removed,
return it to the battlefield under its owner's
control with four +1/+1 counters on it, and each
player sacrifices three lands.