Ashkira, Mother of Nightmares

When Ashkira enters the battlefield or attacks,
sacrifice X creatures. For each creature sacrificed
by Ashkira, put a Nightmare counter on her.
{r}, Remove X Nightmare counters from her: she
deals X damage to any target and X/2 damage to
her controller rounded down.
{u}, Remove X Nightmare tokens from it: you
draw X cards and each opponent
discards X/2 cards rounded up.