X is the number of artifact and/or creature cards in an opponent's graveyard as you cast this spell.
Distribute X +1/+1 counters among any number of target creatures.
Put X +1/+1 counters on any number of target creatures, distributed any way you choose, where X is equal to the number of creatures and artifacts in target opponent's graveyard.
"This is the fun part!"
—Ib Halfheart, Goblin Tactician