Agatha's Soul Cauldron from Wilds of Eldraine (242) is a Mythic Artifact card.
Illustrator: Jason A. Engle
Rules
You may spend mana as though it were mana of any color to activate abilities of creatures you control.
Creatures you control with +1/+1 counters on them have all activated abilities of all creature cards exiled with Agatha's Soul Cauldron.
{T}: Exile target card from a graveyard. When a creature card is exiled this way, put a +1/+1 counter on target creature you control.
