Kayn, the Shadow Reaper

While in the command zone or on the battlefield, whenever you deal damage to an opponent,
add a permanent darkin or shadow counter onto Kayn, the Shadow Reaper.
{t}{2}{u}{b}, Remove 3 shadow counters.
Transform into Kayn, the Shadow Assassin
{t}{2}{r}{b}, Remove 3 darkin counters.
Transform into Rhaast, the Darkin Blade