Karumonix, the Rat King
Legendary Creature — Phyrexian Rat
Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
Other Rats you control have toxic 1.
When Karumonix enters, look at the top five cards of your library. You may reveal any number of Rat cards from among them and put the revealed cards into your hand. Put the rest on the bottom of your library in a random order.
- CMC
- 3
- Mana cost
- Color identity
- B
- Rarity
- rare
- Set
- Phyrexia: All Will Be One Promos
- Price
- $1.06
- EDHREC rank
- #3284
Karumonix, the Rat King lands and immediately poisons every opponent, turning your board of Rats into a clock that bypasses combat math entirely. The five-mana cost is real, but the enter-the-battlefield tutor stapling onto a lord makes it better than Marrow-Gnawer at justifying the slot — you play it for the free poison, and the anthem is the bonus.
Best Commanders
Commanders with the highest synergy
Marrow-Gnawer
Marrow-Gnawer is the definitive Rat tribal commander, and Karumonix, the Rat King earns its 76% inclusion rate by doing two things Marrow-Gnawer can't — distributing poison counters immediately and tutoring another Rat into hand the turn it enters.
Ashcoat of the Shadow Swarm
Ashcoat of the Shadow Swarm cares about Rats dying and entering, so Karumonix, the Rat King slotting in means a free poison trigger and a Rat tutor every time it lands — exactly the density that engine needs.
Wick, the Whorled Mind
Wick, the Whorled Mind copies spells and permanents aggressively, and a second Karumonix, the Rat King trigger means another round of poison counters distributed to all opponents without any additional investment.
Totentanz, Swarm Piper
Totentanz, Swarm Piper generates Rats as a byproduct of opponents losing life, and Karumonix, the Rat King accelerates the poison clock on those same opponents — the two cards are pulling the table toward a loss from two directions simultaneously.
Rat King, Verminister
Rat King, Verminister cares about stacking Rats in play, and Karumonix, the Rat King provides both a tutor to find key pieces and a poison-counter burst that advances the infect-adjacent game plan at no extra cost.
Format Analysis
Where it lives, where it can’t
| Format | Verdict |
|---|---|
| commander | legal |
| legacy | legal |
| modern | legal |
| pioneer | legal |
| standard | not legal |
| vintage | legal |
| pauper | not legal |
| oathbreaker | legal |
Commander is the natural home for Karumonix, the Rat King — Rat tribal has real infrastructure there, and the multiplayer poison trigger punishes all three opponents simultaneously rather than one. In Legacy and Vintage it's legal but irrelevant; five mana is an entire game in those formats, and Rats have no competitive presence to build around. Modern and Pioneer are similarly dead ends — the tribe lacks the redundancy and payoffs to compete at those power levels. Oathbreaker is the one fringe case worth noting: as a signature spell it can't sit in that zone, but as a staple in a Rat-themed Oathbreaker build it functions the same way it does in Commander.
Key Combos
Combo lines featuring this card
Price Context
Current price
$1.06 cheap tier
At $1.06, Karumonix, the Rat King is priced like a bulk rare that happens to be a staple, which means it's an easy include with no financial hesitation. Its 70%+ inclusion rates across multiple Rat commanders suggest the price is stable — high demand, low ceiling, exactly where you want a tribal piece to sit.
Explore
Sources
Mentioned
- Marrow-Gnawer
- Ashcoat of the Shadow Swarm
- Wick, the Whorled Mind
- Totentanz, Swarm Piper
- Rat King, Verminister
Updated . Data from Scryfall, EDHREC, and Commander Spellbook.