Kayn, the shadow reaper

At the beginning of your upkeep put a soul
counter Kayn, the shadow reaper.
At the beginning of your upkeep sacrifice Kayn,
the shadow reaper If he has four or more soul counters on him and search your library for a
card named rhaast, slayer of titans and Kayn, the shadow assassin. Put one onto the battlefield and
the other into exile