Graft is a keyword ability.
It is the Simic mechanic. All creature cards with graft start as 0/0s and come into play with a certain number of +1/+1 counters on them equal to their graft number. (For example, if a card has Graft 6, then it comes into play with 6 +1/+1 counters on it, making it a 6/6.) Whenever another creature comes into play, you may move a counter onto it from the card with graft. Most creatures with graft have an activated ability that supports creatures with +1/+1 counters on them. Graft mechanic is very similar to that of the mechanic in Mirrodin (clockworks: Clockwork Dragon), Darksteel(Arcbounds: Arcbound Overseer) and Stronghold (spike: Spike Breeder)
The mechanic comes from a substance created by the Simic creation of Cytoplasm. Cytoplasm is a mysterious living substance that attaches to the user and feeds of the user's live force. In return, it gives huge power boosts. Cytoplasm usually takes the form of large bubbles. The ultimate creation of cytoplasm is Experiment Kraj. It can leach abilities of any creature with a +1/+1 counter on it. Graft has only been seen on Blue and Green creatures and one land from Future Sight (set) this land is Llanowar Reborn.
- 702.57a Graft represents both a static ability and a triggered ability. “Graft N” means “This permanent enters the battlefield with N +1/+1 counters on it” and “Whenever another creature enters the battlefield, if this permanent has a +1/+1 counter on it, you may move a +1/+1 counter from this permanent onto that creature.”
- 702.57b If a permanent has multiple instances of graft, each one works separately.