Soul, Nightmare Arcanist

Whenever a creature you control dies, you get an experience counter.
Pay 1+X experience counters: mill X cards, then
return a permanent card in your graveyard with
converted mana cost X or less to the battlefield.
Pay 3 experience counters: for each of your
creatures, put either a reach, vigilance, or
deathtouch counter on that creature.
Pay X experience counters: exile target spell with
mana value X. It becomes plotted. X can't be 0.