When Contagion Engine enters, put a -1/-1 counter on each creature target player controls. {4}, {T}: Proliferate twice. (Choose any number of permanents and/or players, then give each another counter of each kind already there. Then do it again.)
Bretagard Stronghold enters tapped. {T}: Add {G}. {G}{W}{W}, {T}, Sacrifice Bretagard Stronghold: Put a +1/+1 counter on each of up to two target creatures you control. They gain vigilance and lifelink until end of turn. Activate only as a sorcery.
Choose a creature type. Return all creatures that aren't of the chosen type to their owners' hands.
{4}, {T}: Target opponent loses 2 life, gets a poison counter, then mills six cards.
Search target opponent's library for an artifact card and put that card onto the battlefield under your control. Then that player shuffles.
Flying, vigilance, deathtouch, lifelink At the beginning of your end step, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
Equipped creature gets +2/+2 and has protection from white and from blue. Whenever equipped creature deals combat damage to a player, put a +1/+1 counter on a creature you control, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.) Equip {2}
Legendary creatures you control get +2/+1 and have ward {1}. Nonlegendary creatures you control get +1/+1.