Poison Counters and Infect in MTG: The Ten Counter Kill

The rule, in full

Ten poison counters and you lose. That is the whole thing, and it is a state-based action, which means it happens automatically the instant the tenth counter arrives. Nobody gets priority, no trigger goes on the stack, and there is no window to respond.

Your life total is irrelevant. Zero life kills you and ten poison kills you, and they are two entirely separate doors out of the game.

Why ten is smaller than it sounds

Here is the number that reframes the mechanic: Commander starts you at 40 life but still kills you at ten poison.

Every other threat in Commander scales with the format. Damage races take twice as long. Burn needs twice as many spells. Poison needs exactly as many counters as it does in a 20 life game.

Put that in clock terms. A creature with infect four connects three times and you are dead, in a format where a four power normal creature needs ten connections. Infect is not twice as good in Commander, it is roughly four times as good, and this is why tables tend to treat an infect player as the immediate threat regardless of what else is happening.

Infect versus toxic

These two keywords solve the same design problem and solve it differently.

Infect replaces damage entirely. A creature with infect deals its combat damage to players as poison counters and to creatures as minus one/minus one counters. It deals no normal damage at all.

Toxic N adds on top. A creature with toxic two deals its usual combat damage to your life total and then gives you two poison counters as well.

The scaling row is the important one. Infect turns every pump spell into a poison counter, which is why infect decks in older formats were built as one-turn combo kills: a single unblocked one power creature plus two pump spells is lethal from ten. Toxic cannot do that, because the toxic number does not grow when the creature grows. That predictability is exactly why Wizards moved to toxic.

Proliferate, and the first counter problem

Proliferate says: choose any number of permanents and players with counters on them, and give each another counter of a kind already there.

The words already there carry the whole mechanic. Proliferate cannot start a poison clock. It can only accelerate one that exists.

So a poison deck has a two part structure:

1. Something that lands the first counter, which must be a creature connecting or a direct poison effect
2. Proliferate effects that turn one counter into many, without needing to connect again

That second half is what makes poison resilient. Once a single counter is on a player, every proliferate you draw is a free poison counter that no blocker can stop and no removal spell can interact with. A player on one poison who thinks they are safe is not.

The clock, turn by turn

Assume you connect once per turn with a creature and add proliferate on top. Starting from zero:

Four connections from a two power creature. Against 40 life, that same creature would need twenty turns. That gap is the entire argument for the mechanic.

What actually stops poison

Because poison ignores life totals, the usual defensive tools are worthless. Life gain does nothing. Fog effects work but only for a turn. What genuinely answers it:

• Removal on the creature, before it connects. Poison decks are creature dependent and often fragile, since infect creatures are small by design.
• Board wipes, for the same reason.
• Protection, which stops the damage being dealt at all, so no counters are given.
• Blocking. Unglamorous, but an infect creature that does not connect does nothing, and infect creatures are usually too small to fight through a real board.

What does not work: gaining life, raising your maximum hand size, anything that cares about damage prevention that only applies to life loss.

Common misconceptions

“Commander uses twenty poison because it uses forty life.” It does not. Ten, always.

“Infect creatures deal normal damage too.” They do not. That is toxic. Infect replaces the damage entirely, which means an infect creature attacking a player at one life does not kill them.

“Proliferate can start a poison clock.” It cannot. There must already be at least one counter.

“Poison counters wear off.” They do not, unlike rad counters. Once landed, assume permanent.

“Infect damage to creatures is normal damage.” It is not. Infect deals damage to creatures as minus one/minus one counters, which is why it kills through indestructible and why the damage does not wear off at end of turn.