Ichor Rats

Mana cost: {1}{B}{B}
Type: Creature — Phyrexian Rat
Power / toughness: 2 / 1
Set: Scars of Mirrodin #67 (uncommon)
Price: $3.60 USD

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
When this creature enters, each player gets a poison counter.

Ichor Rats has 2 printings, first in Scars of Mirrodin (2010). EDHREC ranks it #3,294 among Commander cards. It appears most in Atraxa, Praetors' Voice decks (14,694 on EDHREC). 1 public deck on TCG runs it. It has 7 official rulings.

Legality

commander: legal
legacy: legal
vintage: legal
pauper: not legal
modern: legal
pioneer: not legal
standard: not legal
brawl: not legal

Public decks that run Ichor Rats

Corrupting Influence - Phyrexia: All Will Be One Commander, led by Ixhel, Scion of Atraxa

Commanders that run Ichor Rats most

Deck counts from EDHREC.

Atraxa, Praetors' Voice: 14,694 decks
Ixhel, Scion of Atraxa: 5,065 decks
Karumonix, the Rat King: 4,782 decks
Vishgraz, the Doomhive: 2,812 decks
Skithiryx, the Blight Dragon: 2,188 decks
Ingris Stingerquill: 1,779 decks
Marrow-Gnawer: 1,664 decks
Brimaz, Blight of Oreskos: 1,375 decks

Often played with Ichor Rats

Cards that show up in the same decks on EDHREC.

Rulings

2011-01-01: A player who has ten or more poison counters loses the game. This is a state-based action.
2011-01-01: If Ichor Rats's last ability causes each player to have ten poison counters, the game is a draw.
2011-01-01: Damage from a source with infect is damage in all respects. If the source with infect also has lifelink, damage dealt by that source also causes its controller to gain that much life. Damage from a source with infect can be prevented or redirected. Abilities that trigger on damage being dealt will trigger if a source with infect deals damage, if appropriate.
2011-01-01: If damage from a source with infect that would be dealt to a player is prevented, that player doesn't get poison counters. If damage from a source with infect that would be dealt to a creature is prevented, that creature doesn't get -1/-1 counters.
2011-01-01: Damage from a source with infect affects planeswalkers normally.
2011-01-01: Infect's effect applies to any damage, not just combat damage.
2011-01-01: The -1/-1 counters remain on the creature indefinitely. They're not removed if the creature regenerates or the turn ends.