Offering of the Skeleton

Sacrifice a creature: Add one mana of any color.

Creatures don't untap during their controllers' untap steps. Whenever a creature enters, untap all creatures.

As an additional cost to cast this spell, sacrifice a creature. Add X mana in any combination of and/or , where X is the sacrificed creature's mana value.

Whenever a nontoken creature you control enters, you may pay . If you do, create a token that's a copy of that creature, except it has haste and "At the beginning of the end step, sacrifice this permanent."

When this creature dies, return it to its owner's hand.

When this creature enters, you may exile an instant card from your hand. , : Copy the exiled card. You may cast the copy without paying its mana cost. X is the mana value of the exiled card.