Ojetai, Guardian of Drakos

Flying, Lifelink, Indestructible
At the beginning of your upkeep, put an age
counter on Ojetai, Guardian of Drakos. then if
Ojetai, Guardian of Drakos has 5 or more age
counters, sacrifice Ojetai, Guardian of Drakos
and the city falls (sacrifice all non-creature
permanents you control)
Whenever a creature attacks you, it's controller
sacrifices a permanent.