I shadow-DM my little brother's D&D game, helping him plan story arcs and dramatic battles. His next session will be a boss fight, where the sorcerer PC will be facing off against their evil spellcaster mother. He thought it would be both dramatic and thematic for the two of them to fight in a "mage duel" while the rest of the party fought the enemy horde, which sounded bad-ass to me. But how should we represent this?

Right off the bat, "just use normal spellcasting" was out. It's boring, and would largely just be a matter of "try to cast, get counterspelled, they try to cast, you counterspell, etc" until one of them runs out of high-level spells. Boring and frustrating, far from dramatic, and in the meantime the other characters might be actually beating up the mom in melee, which isn't thematically appropriate either.

Bro recalled that Mage Hand Press, his favorite 5e imprint, had published a simple Mage Duel ruleset, as part of a larger set of "wizarding contests". This looked like a good starting point, but it was clearly designed to be a fast, simple resolution mechanism as a small part of a larger roleplaying session around a wizarding carnival or tourney. It really didn't have any strategic depth (just choose your highest-level slot each time and hope you roll well), which didn't suit our dramatic boss fight.

So we iterated on this a bit, and ended up with something that I think will be quite fun at the table. It has some actual strategic choice, rewards predicting the opponent's moves, and lets the duel have an effect on the rest of the battle being waged around them.

Dramatic Mage Duels!

At the start of each round, before anyone else takes actions, the two duelists secretly choose a spell slot they want to expend, and a dueling stance. They reveal both, then make an opposed Arcana check, using their spellcasting ability. Each duelist gets a bonus to this check equal to half the chosen slot's level (round down, as usual). The loser of the opposed check takes (winner's slot)d6 damage. A tie causes both characters to take (their slot)d6 damage, as the spells rebound.

There are three dueling stances: attack, shield, and tricky. The two opponent's stances are compared in a rock-paper-scissors fashion: attack beats tricky, tricky beats shield, and shield beats attack. If one of the characters win, they get advantage on the Arcana check. (Ties have no effect.)

In addition to the direct damage the duelists deal to each other, the chaotic energies of their duel spill out and buff/debuff the rest of the combatants. Each duelist also makes a roll on the Chaotic Buff and Chaotic Debuff tables, adding their expended slot's level to the Buff roll and subtracting it from the Debuff roll. Everyone else on the duelist's side of the combat benefits from the rolled buff and suffers the rolled debuff.

Finally, the chosen stance has additional effects. If you choose Attack, you deal 3d6 damage to your opponent (whether you win or lose the Arcana contest). If you choose Tricky, you roll on the Buff table twice and choose the result you prefer. If you choose Shield, you roll on the Debuff table twice and choose the result you prefer.

The duel is over when either duelist yields, or dies.

Buff And Debuff Tables

These are taken with only slight modifications from the very nice Sorcerer tweak by SwordMeow (direct link to PDF), which presents a much more interesting Wild Magic Sorcerer than the original.