Devil's Deal
Devil's Deal, also often referred to as a "deal with the devil", is a slang term used by Magic R&D to describe permanents that start helping you but have the potential to hurt you in the end. These are most often enchantments, but occasionally show up in other forms on creatures.[1]
Description
Cards with a devil's deal have a powerful effect or significant Power/Toughness but have a downside that is equally strong. These types of cards encourage players to end the game relatively quickly after being cast lest they cause their controller to lose the game. The mechanic is primary in black, because it is the color of "power at any cost."
This mechanic caused Design to heavily limit the ability of black cards to remove enchantments from the battlefield, even after determining black could remove opposing enchantments starting with Pharika's Libation and Mire's Misery. Doing so preserved the flavor of the mechanic being a binding deal but caused black to have issues in the limited environments of enchantment-heavy sets. By the release of Duskmourn: House of Horror, design had reversed their stance due to the realization that very few enchantments with a devil's deal were being made anyway.[2]
Example
Example 1
Demonic Pact 
Enchantment
At the beginning of your upkeep, choose one that hasn’t been chosen —
• Demonic Pact deals 4 damage to any target and you gain 4 life.
• Target opponent discards two cards.
• Draw two cards.
• You lose the game.
Example 2
Lord of the Pit 
Creature — Demon
Flying, trample
At the beginning of your upkeep, sacrifice a creature other than Lord of the Pit. If you can’t, Lord of the Pit deals 7 damage to you.
7/7
References
- ↑ Mark Rosewater (June 5, 2017). "Mechanical Color Pie 2017". magicthegathering.com. Wizards of the Coast.
- ↑ Mark Rosewater (September 09, 2024). "Has Black's design philosophy changed on its ability to remove enchantments?". Blogatog. Tumblr.