Byleth, Wings of Hegemon

First strike, reach, trample.
When Byleth, Wings of Hegemon enter's the battlefield place 1 pulse counter on it.
During your end phase, if one or more creatures
you controlled died this turn you may remove 1
pulse counter to put all permanents on the battlefield that left the battlefield this turn.
If you do, exile Byleth, Wings of Hegemon, then
return it to the battlefield transformed
under their owner's control.