Summary
There are plenty of ways to win a game inMagic: The Gathering. Most of the time you’re reducing your opponent’s life total down to zero, or perhaps even more common, placing your opponents in a state where there’s little to no chance of winning.
Other paths to victory might set you on a path to mill your opponents out, while others might combo them into oblivion. One method that is surprisingly consistent is by poisoning your opponent until they lose the game.

6How Does Poison Work?
An Older Mechanic Revitalized
Poison is a tricky mechanic for you to work with, but can be incredibly difficult for your opponents to do much about once the engine starts going. Poison is tracked by counters, and once a player has ten poison counters they immediately lose the game.
If you’re playing a poison-based deck, the name of the game is to stick at least one poison counter on a player and find all sorts of ways to tick that counter up to ten.

5Karumonix, The Rat King
Bring The Infestation
One of the more interesting Commanders on this list, Karumonix, the Rat King is a pretty big divergence from other poison-based legendary creatures on this list, but that doesn’t make him any less impressive.
This deck works more on a Rat theme rather than a straight poison one since Karumonix gives your other Rat creatures toxic 1. Toxic works by giving an opponent poison counters equal to the number associated with the keyword, and in this case, it is one.

So all you have to do with Karumonix is build a fairly straightforward Phyrexian Rat deck, find a few ways to get them to slip through some combat damage, and start watching those poison counters tick up.
4Skithiryx, The Blight Dragon
Infect The World
One of the most intimidating commanders to face down when considering a poison-based Commander,Skithiryx, the Blight Dragon slaps poison countersdown on a highly aggressive mono-black creature.
Skithiryx is a five-mana 4/4 creature with flying and infect, giving it some evasion in the air and helping to keep your opponent’s board clear with -1/-1 counters. Infect is somewhat similar to Toxic from Karumonix but with a fundamental difference. If Skithiryx deals damage to a creature, that creature gets -1/-1 counters, making it perpetually weaker turn after turn, if it even lasts that long. It also deals damage in the form of poison counters instead of regular combat damage to players, quickly racking up those poison counters.

Helping to push those counters, Skithiryx gets two abilities to help bring you to victory. The first gives Skithiryx haste, letting you attack the turn it comes out, and the second is to regenerate Skitheryx, which is a slightly outdated mechanic that keeps it safe through most actions.
It only takes three hits to a player to knock them out through infect damage with Skithryx, fewer if you have a way to pump up his power by even one point.

3Ixhel, Scion Of Atraxa
A Latticework Of Toxicity
One of the more complicated commanders dedicated to poisoning out your opponents, Ixhel, Scion of Atraxa comes loaded with keywords and abilities to poison your opponents out of the game. Ixhel naturally has toxic 2, dishing out two poison counters when you deal damage with it to a player.
Then, at the start of your end step, you get to take a look at the top of their library if they have three or more poison counters. You can then take one of those cards and play it for free so long as they stay exiled, spending mana as you please, so you can cast spells that don’t match your Commander’s color identity.

Ixhel encourages poisoning your opponents somewhat equally, as you want to make sure each of your opponents has at least three poison counters. That’ll give you at least three cards from your opponent’s deck to work with, and let you cast those cards from exile for the entirety of the game. Once you’re in a good enough spot by playing your opponent’s decks, you can finish off the poison job with Ixhel’s toxic 2.
2Fynn, The Fangbearer
Deathtouch Has Never Been Deadlier
Like Skithiryx, Fynn is a relatively straightforward Commander, one that can be exceptionally explosive right out of the gate, or be a slow grind to death. This two-mana uncommon Commander is a bit of a rarity among Commanders. Fynn, the Fangbearer is a 1/3 creature with deathtouch, but the most relevant bit of the card is their second ability.
Anytime a creature you control with deathtouchdeals combat damage to a player, that player gets two poison counters. Since most players don’t want to offer sacrificial lamb to a random 1/1 with deathtouch, the trade-off is that all you have to do is hit them five times to get to that magical ten-poison counter.
Any creature becomes a threat with Fynn out, and even one poison counter on your opponent can be deadly thanks to any number of proliferation effects.
1Atraxa, Praetors' Voice
The Proliferation Queen
Speaking of Proliferation, Atraxa can quickly turn the tide in a battle just by sitting out on the battlefield for a few too many turns. The main way you win with Atraxa is through her final ability, the one that lets you proliferate every tun.
You need to stick at least one poison counter on each of your opponents, but that shouldn’t be too difficult, seeing as you have access to four of the five colors of Magic. If you happen to lose Atraxa or can’t seem to get her to stick her around for that end step trigger,you have some of the best proliferation effects in Magic. You also get quite a few ways to ensure that you can sneak some bonus triggers and poison counters in through simple spells like Prologue to Phyresis, which just gives each opponent a poison counter, and Blighted Agent, an unblockable creature with infect.