The duel begins, and you roll for inititiative. If the person who wins initiative chooses to start right away, you follow normal combat rules. But if the first person readies an action and chooses to wait for his opponent to make the first move, then his opponent also readies an action, things can slow down. Imagine gunslingers, waiting for the right moment to go.
Whenever it finally comes time to start the duel, the two mages do one of the following:
- Make opposed bluff checks.
- One makes a bluff check opposed by a sense motive check.
- Make opposed sense motive checks.
If you have add your Initiative modifier to this check. Whoever wins goes first.
During the duel you can ready actions just like in normal combat if you want to counter a spell, or if you have the Reactive Counterspell feat you can use that. Also, you can feint with Bluff to do the following things:
- As a move action you can attempt to hide the spell you're casting. You make a Bluff check, and then the DC of the Spellcraft check to determine the spell you cast this turn is either the normal DC, or the result of your Bluff check, whichever is higher. If you have the Spellfeint feat, you can make this bluff as a free action whenever you cast a spell.
- As a standard action you can try to fake out your opponent and make him think you're casting a spell when you're actually not. This is a good way to get opponents to waste a counterspell. Make an Bluff check opposed by your opponent's Sense Motive check. If you win, your opponent's readied action goes off now, assuming he was readying an action to respond to you casting a spell. The drawback is that your opponent still has the higher initiative, so he can just try to counter you again next round. If you have the Spellfeint feat, though, you can make this Bluff as a move action instead of a standard action, which lets you both bluff and cast a spell in the same round.
- As a standard action you can make it look like you're casting a different spell than you actually are. Then whatever spell you cast the next turn will look like whatever you're trying to fake it as. This requires a Bluff check (DC 25 + spell level you're emulating). If you fail the Bluff check, you must make a Concentration check (DC 15 + spell level of the actual spell) or your concentration is disrupted and you lose your spell. If you have the Spellfeint feat, though, you can make this Bluff as a move action instead of a standard action, which lets you both bluff and cast a spell in the same round.
I would then suggest making a simple feat that gives +1 to Bluff and Sense Motive checks and makes it a class skill.
Spell Duelist
You are skilled at magical duels.
Prerequisite: Training from a spell duelist, ability to cast 1st level spells.
Benefit: You gain a +1 bonus to skill checks with Bluff and Sense Motive. Bluff and Sense Motive are class skills for you.
Spellfeint
Your spellcasting is subtle and cunning.
Prerequisite: Dex 13+, Bluff 5+ ranks.
Benefit: You can make a Bluff check to hide what spell you are casting as a free action, instead of a move action. You can attempt to attempt a feint to make an opponent waste a counterspell as a move action instead of a standard action. You can also attempt to make the spell you're casting seem to be a different spell as a move action instead of a standard action.