Sion, the Undead Juggernaut

Sion's toughness is equal to the number of creatures in all graveyards.

When Sion dies, if Sion was attacking and wasn't Goaded, there is an additional combat step after
this one. Return Sion to the battlefield, with
a finality counter. He has Haste, Decayed and is Goaded. No other creatures can attack this turn except Sion.