Scavenge

Scavenge is a keyword ability that was introduced in Return to Ravnica as the mechanic for the Golgari guild. Dragon's Maze added 2 cards with scavenge. It basically reads as a variation on flashback that makes target creature bigger.

Description
Scavenge is an activated ability that functions only while the card with scavenge is in a graveyard. “Scavenge [cost]” means “[Cost], Exile this card from your graveyard: Put a number of +1/+1 counters equal to the power of the card you exiled on target creature. Activate this ability only any time you could cast a sorcery.”

History
The first set after the Return to Ravnica block to feature Scavenge was Commander 2020 (Boneyard Mycodrax).

Rulings

 * Exiling the creature card with scavenge is part of the cost of activating the scavenge ability. Once the ability is activated and the cost is paid, it's too late to stop the ability from being activated by trying to remove the creature card from the graveyard.