Ruby, the Spellkeeper

{u}{g}: exile a card from your hand. if you do,
return all other spells exiled with Ruby to their
owner's hand.
Whenever a spell with converted mana cost less
than the exiled spell's mana cost is cast, you may
exile that spell. If you do, return all other spells
exiled with Ruby to their owner's hand.
{t}{x}: Cast the exiled spell without paying its mana
cost. X is equal to that spell's converted mana cost minus the amount of +1/+1 counters among creatures you control