When Contagion Engine enters the battlefield, put a -1/-1 counter on each creature target player controls. {4}, {T}: Proliferate, then proliferate again. (Choose any number of permanents and/or players, then give each another counter of each kind already there. Then do it again.)
NM-Mint - $17.30
Lightly Played - $16.40
Moderately Played - $15.50
Heavily Played - $13.80
Damaged - $11.20
NM-Mint Non English - $17.30
Lightly Played Non English - $16.40
Moderately Played Non English - $15.50
Heavily Played Non English - $13.80
Damaged Non English - $11.20