Fiendish Duo
Creature — Devil
First strike (This creature deals combat damage before creatures without first strike.)
If a source would deal damage to an opponent, it deals double that damage to that player instead.
- CMC
- 6
- Mana cost
- Color identity
- R
- Rarity
- mythic
- Set
- Murders at Karlov Manor Commander
- Price
- $2.58
- EDHREC rank
- #3595
Fiendish Duo doubles all damage dealt to players — on a 5/4 first strike body for five mana — making it one of the most efficient damage-doubling effects in Commander. Heartless Hidetsugu becomes a one-shot kill with it in play, and Nelly Borca, Impulsive Accuser turns every forced combat into a lethal math problem for the table.
Best Commanders
Commanders with the highest synergy
Nelly Borca, Impulsive Accuser
Nelly Borca, Impulsive Accuser forces opponents to attack each other, and Fiendish Duo ensures that every point of damage those combats deal is doubled — turning a political engine into a reliable table-kill clock.
Zurzoth, Chaos Rider
Zurzoth, Chaos Rider pushes opponents to draw extra cards and deal themselves damage through Devil triggers; Fiendish Duo doubles every point of that incidental ping, collapsing life totals before opponents stabilize.
Kratos, God of War
Kratos, God of War punishes opponents for having creatures and deals direct damage as part of his gameplan; Fiendish Duo doubles that output, compressing the number of activations needed to close a game.
Raphael, Fiendish Savior
Raphael, Fiendish Savior leads a Demon and Devil tribal shell where a lot of incidental damage flies around; Fiendish Duo amplifies every one of those triggers, turning chip damage into serious pressure.
Red Death, Shipwrecker
Red Death, Shipwrecker deals damage to opponents as a cost and condition of his abilities; Fiendish Duo makes each of those damage instances hit twice as hard, accelerating the race to lethal.
Format Analysis
Where it lives, where it can’t
| Format | Verdict |
|---|---|
| commander | legal |
| legacy | legal |
| modern | not legal |
| pioneer | not legal |
| standard | not legal |
| vintage | legal |
| pauper | not legal |
| oathbreaker | legal |
Fiendish Duo is a Commander card through and through — the damage-doubling effect is most powerful in a multiplayer game where three opponents are all taking hits simultaneously, and five mana is a perfectly acceptable cost when the payoff scales with the whole table. In Legacy and Vintage, where it's technically legal, a five-mana enchantment creature that doesn't generate immediate card advantage has no competitive footing against the speed of those formats. Oathbreaker follows the same logic as Commander at smaller scale — still a reasonable inclusion in any Oathbreaker deck built around burn or direct damage. Outside those formats, Fiendish Duo simply isn't legal, and even if it were, the design is clearly optimized for the longer, multiplayer game Commander provides.
Key Combos
Combo lines featuring this card
Delina, Wild MageKediss, Emberclaw FamiliarFiendish Duo
Near-infinite damage
View on Commander Spellbook ↗Price Context
Current price
$2.58 cheap tier
At $2.58, Fiendish Duo sits comfortably in the cheap tier for an effect this powerful — damage doubling at this rate is rare, and the price reflects solid demand without speculation. It's a staple in its archetypes rather than a fringe pickup, so the price is unlikely to crater.
Explore
Sources
Updated . Data from Scryfall, EDHREC, and Commander Spellbook.