Agatha of the Vile Cauldron 

Legendary Creature — Human Warlock
Activated abilities of creatures you control cost {X} less to activate, where X is Agatha's power. This effect can't reduce the mana in that cost to less than one mana.
{4}{R}{G}: Other creatures you control get +1/+1 and gain trample and haste until end of turn.
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Cards that do something similar expected a card that isn't here?
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Biomancer's Familiar 82%
$1.57#3186
"Activated abilities of creatures you control cost {2} less to activate. This effect can't reduce the mana in that cost to less than one mana."