Butterfly

Butterfly's under your control get +2/+2 and
Wither
(There must be 2 Butterfly's upon the battlefield)
Butterfly's under your control get +5/+5 and
Wither
(There must be 3 Butterfly's upon the battlefield)
Butterfly's under your control get +8/+8 and
Wither
(There must be 4 Butterfly's upon the battlefield)