Each creature gets +1/+1 for each other creature on the battlefield that shares at least one creature type with it. (For example, if two Goblin Warriors and a Goblin Shaman are on the battlefield, each gets +2/+2.)
"Hup, two, three, four,
Dunno how to count no more."
NM-Mint - $15.70
Lightly Played - $14.90
Moderately Played - $14.10
Heavily Played - $12.50
Damaged - $10.20
NM-Mint Non English - $15.70
Lightly Played Non English - $14.90
Moderately Played Non English - $14.10
Heavily Played Non English - $12.50
Damaged Non English - $10.20