Kayn, The Shadow Reaper

If Kayn, The Shadow Reaper deals combat
damage, put that many Transformation
counters on Kayn, The Shadow Reaper.
At the begining of each endstep, if there are 10
or more Transformation counters on Kayn,
The Shadow Reaper, sacrifice it and search
your library or graveyard for either Kayn, The
Shadow Assassin or Rhaast, The Darkin Scythe,
and put it onto the battlefield as your new
commander.