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Artifact
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.)
Creature
Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.) Other creatures you control with infect get +1/+1. Whenever you cast a creature spell with infect, target player gets a poison counter.
Flying, vigilance, toxic 2 Corrupted — At the beginning of your end step, each opponent who has three or more poison counters exiles the top card of their library face down. You may look at and play those cards for as long as they remain exiled, and you may spend mana as though it were mana of any color to cast those spells.
At the beginning of your end step, for each player, put a +1/+1 counter on up to one target creature that player controls. Each creature with one or more counters on it can't attack you or planeswalkers you control unless its controller pays {X}, where X is the number of counters on that creature.
Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.) At the beginning of your upkeep, create a 1/1 green Phyrexian Insect creature token with infect for each poison counter your opponents have.
Toxic 1 (Players dealt combat damage by this creature also get a poison counter.) Skrelv, Defector Mite can't block. {W/P}, {T}: Choose a color. Another target creature you control gains toxic 1 and hexproof from that color until end of turn. It can't be blocked by creatures of that color this turn. ({W/P} can be paid with either {W} or 2 life.)
Flying If you would proliferate, proliferate twice instead. {1}{U/P}{U/P}, Remove three counters from among other artifacts, creatures, and planeswalkers you control: Put an indestructible counter on Tekuthal, Inquiry Dominus. ({U/P} can be paid with either {U} or 2 life.)
Trample, haste If you would put one or more counters on a permanent or player, put twice that many of each of those kinds of counters on that permanent or player instead. If an opponent would put one or more counters on a permanent or player, they put half that many of each of those kinds of counters on that permanent or player instead, rounded down.
Enchantment
At the beginning of each opponent's end step, if you didn't lose life this turn, you may put a quest counter on Luminarch Ascension. (Damage causes loss of life.) {1}{W}: Create a 4/4 white Angel creature token with flying. Activate only if Luminarch Ascension has four or more quest counters on it.
Instant
Until your next turn, your life total can't change and you gain protection from everything. All permanents you control phase out. (While they're phased out, they're treated as though they don't exist. They phase in before you untap during your untap step.) Exile Teferi's Protection.
Land
Planeswalker
Compleated ({G/W/P} can be paid with {G}, {W}, or 2 life. If life was paid, this planeswalker enters with two fewer loyalty counters.) +1: Reveal the top card of your library. If it's a creature or planeswalker card, put it into your hand. Otherwise, you may put it on the bottom of your library. −3: Distribute three +1/+1 counters among up to three target creatures. They gain vigilance until end of turn. −6: You get an emblem with "Whenever you cast a creature or planeswalker spell, target opponent gets two poison counters."
Compleated ({B/P} can be paid with {B} or 2 life. If life was paid, this planeswalker enters with two fewer loyalty counters.) 0: You draw a card and you lose 1 life. Proliferate. −2: Target creature becomes a Treasure artifact with "{T}, Sacrifice this artifact: Add one mana of any color" and loses all other card types and abilities. −9: If target player has fewer than nine poison counters, they get a number of poison counters equal to the difference.
Sorcery
Exile target creature you don't control. For each creature exiled this way, its controller searches their library for a basic land card. Those players put those cards onto the battlefield tapped, then shuffle. Overload {4}{W}{W} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")
Maybeboard
Trample, toxic 1 Whenever one or more creatures you control deal combat damage to one or more players, proliferate. Corrupted — At the beginning of your end step, if an opponent has three or more poison counters, draw a card, then you may put a land card from your hand onto the battlefield.
Defender (This creature can't attack.) Flying Whenever Mindbender Spores blocks a creature, put four fungus counters on that creature. The creature gains "This creature doesn't untap during your untap step if it has a fungus counter on it" and "At the beginning of your upkeep, remove a fungus counter from this creature."