Aggressive Hex

Creature spells you cast this turn have riot.
Add one mana of any color. Spend this mana
only to cast creature spells.
(as a hex resolves, an opponent of your choice shuffles it into their library face up instead of
you putting it into your graveyard. If this card would leave a library other than its owner's, its owner exiles it instead and may cast it for as
long as it remains exiled.)