I would like to volunteer Brannor as he perhaps stands the best odds based upon Armor Class alone given our resident barbarian has no rage left and we haven't had the time to recover those. The only part that concerns me is that this seems fairly life and death, but there's no reason we cannot attempt to bargain that out - the dragonkin gets what it wants in a fight, the prisoners go free, and it isn't to the death, just to defeat. That's of course assuming it has any sense of honor or would not just be willing to go back on its words. Consider me skeptical of both those.

I am wary that they would put a lethal encounter in here in a solo fight between a 1st level character and whatever level the half-dragon is; my guess is he's a subordinate boss and we're meant to find that out by squaring off with him. The most Brannor can do is attempt to start the combat by already having a readied Dodge action to mitigate the enemy winning initiative, which he likely will or at least have a fifty-fifty on. I am [i]hopeful[/i] the enemy is going to use a one handed weapon so if Brannor does get hit he might survive it, but there's only so much I can do.; Orchid's disarmament plan should work brilliantly as the two should be close to Strength score meaning fair enough odds, unless of course he has a two-handed weapon.

I doubt we can legitimately kill him as is - he might also have plot armor.

Either way, the biggest areas we need to concern ourselves with are getting the prisoners set free and the fight not being to the death. Having [i]everyone[/i] train weapons on him, all of the guardsmen and soldiers as well as the party, should be a major deterrent to any shadiness. I am assuming he's tough to kill, but a barrage like that should be close to mortal or certainly look it. I am assuming [@Hekazu] will make it more real and less game-y in that regard; twenty men with bows and a band of other adventurers all pointing weapons at you and set to kill you if you cheat or renege on your deal should work.

An army three times the size he might have as well but that means [i]nothing[/i] in a close quarters battle as would be with a keep. You would just need channel them into a fatal funnel and force them to keep fighting you through the gauntlet of death; preferably doorways no bigger than ten feet. Odds are a bunch of kobolds won't survive that and any humans in that army - I am assuming half - are not going to be willing to dive headlong into it. This is of course assuming Greenest's guard have any idea what they're doing. I [i]hope[/i] this isn't the case either because we've still yet to rest and heal, but it might just be an encounter we're meant to flee from after whatever happens with the half-dragon.