Shadow Planar Rift

At the beginning of your upkeep put a charge
counter on Shadow Planar Rift for each leyline
you control.
At the beginning of your upkeep create a 1/1
black Elemental creature token for each charge
counter on Shadow Planar Rift.
Whenever Shadow Planar Rift has 10 or more
charge counters on it, sacrifice it.