Gishki Nekromirror

Select a Gishki Ritual creature in your hand or
command zone with Ritual Summon X.
Either discard any number of creature cards and
sacrifice any number of creatures with total mana
value X, or target opponent sacrifices
target nontoken creature they control. Cast that
Ritual creature and you lose X life.
If this card is in your graveyard, you may pay {u/b}{u/b}{u/b}: Put this card on the bottom of
your library, then put target Gishki creature in
your graveyard on top of your library.