Duels, but not the Wizard kind

Il Fior di Battaglia (public domain)

A one-on-one showdown should be treated differently than the standard tactical group combat we see most often. Standard RPG combat often suffers the complaint that players and foes alike end up fixed in place, repeatedly chipping away at a pool of hit points until one side eventually and suddenly keels over. Now this isn't always the case, but nowhere is this more true than a single-opponent melee face-off. I mean, what are you supposed to do other than hit each other?

A duel deserves the spotlight and a closer focus. It deserves to feel like a choreographed swordfight rather than just another battle scene. In fact, as part of a combat it can be incredibly satisfying to switch between these two modes of play each turn, the duel occurring within the larger combat.

Here is a system for dueling in DCC based on spell duels and the Feint/Parry/Push system over at Cavegirl's Game Stuff. It's supposed to be pretty intense and swingy, and to snowball after a few rounds. It's also intended to be a little complex and crunchy, like spell duels.

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Dueling Basics

A duel begins when two combatants agree to one-on-one combat. At the beginning of the duel, each duelist places down a d20 with the 10 face-up. This is the momentum tracker.

In each Round of combat while a duel is active, both duelists act simultaneously on whichever of their initiatives is first. At the beginning of the Round, they each secretly decide and write down (or use a face down card, or some other secret method) whether their tactic for the turn will be Aggressive, Defensive, or Deceptive. These are revealed and compared in a rock-paper-scissors style triangle.

Aggressive > Defensive > Deceptive > Aggressive

If you chose the winning tactic, you gain the following listed bonus and your momentum increases by 1. If you both chose the same tactic, you both gain the bonus and both lose 1 momentum.

• Aggressive grants +1d6 to damage (or just +1d3 for unarmed or improvised attacks)
• Defensive grants +3 to AC.
• Deceptive grants +1d to your attack roll.

Both duelists now attack and deal damage simultaneously, the difference between their momenta modifying each attack roll. It is entirely possible for them both to kill each other if they both strike.

Striking the opponent increases your momentum by 1. Being struck decreases your momentum by 1. 

The duel ends when one duelist accepts the other's yield, a duelist is incapacitated, or the duel is interrupted.

Movement

The combatants are locked within melee range of each other. Whichever combatant wins the first tactic has positional advantage during the round and may move both themselves and their interlocutor up to half of their movement speeds. This may be used to move and rotate the duel at will. Being forced into direct danger can be prevented with a Reflex save, DC equal to the first attack roll.

Multiple Attacks

Skilled combatants are capable of much more tactical complexity. Each attack during a Round is also a chance to change tactic, performing more complex maneuvers such as a deceptive strike followed by an aggressive attack to the opening. Each successful tactic's bonus remains until the end of the Round, applying to all remaining attacks. Bonuses stack.

The pace is set by the character with the most actions, so the slower character must decide (at Round start) which of those attacks to respond to with their own attacks. For instance, in a duel between characters with 3 and 2 attacks respectively, the duelist with 2 attacks must choose which two "sub-Rounds" they make their attacks/tactical changes on. The first tactic always applies from the beginning of the Round.

Clashing

If two duelists roll the exact same result on a simultaneous attack, they Clash. Both attacks miss (unless otherwise specified), but an additional effect occurs. Roll 1d6.

1. Weapons shatter. If one weapon is of a clearly weaker material than the other, it is sundered and the attack passes through it, hitting. If the two weapons are of comparable material, they are both shattered in the hands of the duelists. If a weapon is magic, instead of shattering, a burst of magical energy emanates from it dealing 1d6 damage to anyone within 5' (including both duelists). This may have special effects based on the nature of the magic weapon.
2. Bind. The duelists' weapons interlock and the combatants are forced into a contest, each attempting to manipulate the other's weapons with their own. Roll a contested check, with the ability used depending on the tactic (Aggressive:Strength, Defensive:Stamina, Deceptive:Agility). The winner of the contest rolls 1d3: (1) strike opponent, (2) disarm opponent, (3) knock opponent prone.
3. CLANG. A resonant sound echoes from your weapons as an unstoppable force meets an immovable object. All creatures within 60' must make a DC 15 Will save or be distracted, startled, or awestruck, taking a -1d penalty to any checks for the rest of the Round and having a 50% chance of dropping their weapon. It does not matter what the weapons are made of - even bare fists colliding produces a supernatural sonic blast.
4. Overbalanced and entangled. The combatants collide, both becoming prone and getting stuck in a grapple with each other. A Strength contest determines who has hold of the other.
5. Collateral damage. The momentum of battle forces the combatants to move up to half movement speed, into melee range of a nearby target. One of you hits them. Decide randomly who hits (and who gets hit, if applicable).
6. Swords dance. Your weapons bounce and both parties attempt to take advantage of the opening. In the adrenaline and intense focus of the battle, both combatants get 1d4 (roll once, both use same result) additional dueling attacks.