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."
Near Mint - $17.75
Lightly Played - $16.75
Moderately Played - $14.25
Heavily Played - $10.75
Damaged - $9.00
Near Mint Non-English - $17.75
Lightly Played Non-English - $16.75
Moderately Played Non-English - $14.25
Heavily Played Non-English - $10.75
Damaged Non-English - $9.00