Work in progress: basically, the DM has a "hand" of cards to play (per encounter? per session? maybe the DM gets more depending how many PCs there are?). These represent twists of fate, enemy preparation, or just plain fudging. The DM plays the cards, usually as an immediate action, to affect the flow of combat (and perhaps non-combat), using meta-game knowledge, in order to keep the game interesting.

Example cards:

• Decoy: If a Villain drops below half health, swap identities with a Minion; it turns out the "villain" was merely a decoy, and the true mastermind was disguised as a lowly goon. Requires a living minion at the time of the "Villain"'s death
• Reinforcements: New enemies join the battle; choose either a number of minions equal to the PC's number, or one elite per 2 PCs.
• Level Up!: An enemy suddenly "levels up", restoring full hit points and gaining an Elite Trait. Villainous characters merely regain 1/2 of max HP.
• Who Put That There?: PC suddenly trips on an object they didn't see (Dex save mitigates to unbalanced (no Dex bonus to AC until next turn, can't threaten an area)).
• Turncoat: Secret! Next time a PC summons a minion, the minion had a previous bargain with the Villain or Leader, and is bound to sabotage the PC's plans.

May possibly use a Hearthstone-esque point system to differentiate minor and major cards.