The Blood Maidens

Menace, trample, vigilance
The Blood Maidens gain +1/+1 for each other creature you control. If you control seven or more creatures, swap the power and toughness of The Blood Maidens.
Whenever a nontoken creature enters the battlefield under your control, you may pay {p/w}{p/w}{p/g}{p/g}. If you do, put a token into play that's a copy of that creature.