Erebus, The First Heretic

Whenever you cast a Demon or Devil spell, create X 0/1 red Cultist creature tokens,
Where X is that spell converted mana cost.
{x}{u}{b}, {t}: Sacrifice X Cultist draw X cards.
{4}{r}{r}, {t}: Cultist you control gain +2/0
until end of turn.
{x}{x}{b}{b}{b}, {t}: Sacrifice X Cultist, create X
5/5 black Demons with flying.