Orikhos Alametri

Indestructible
While your life total is 15 or higher, Orikhos Alametri isn't a creature.
Orikhos Alametri's power and toughness are each equal to the number of cards in all graveyards.
At the beginning of your upkeep, sacrifice Orikhos Alametri unless you pay X, where X is half your life total rounded up.