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."
—Mogg march
Near Mint - $29.00
Lightly Played - $23.20
Moderately Played - $20.30
Heavily Played - $17.40
Damaged - $14.50
Near Mint Spanish - $29.00
Lightly Played Spanish - $23.20
Moderately Played Spanish - $20.30
Heavily Played Spanish - $17.40
Damaged Spanish - $14.50