Necronium Gate

Creatures you control become black and are Horrors in addition to their other creature types.
Sacrifice ten Horrors, {t}: until end of turn, you may cast any creature from your hand without paying its mana cost.
"The Haltimulicrum housed a horrific truth, and
when it was discovered, we were already too late to stop it... the Cannibrae are here."
- Saracine, Researcher