I have been running a sandbox campaign for some time now. Current group expected to attend next game:
Rogue 9
Sorc/Dragon Disciple 9
Cleric 8 (this cleric is so min/maxed he heals like a champ + the group pooled to get him items to increase his channels and he took an achievement feat also that adds to it, so healing is a non issue)
Inquisitor 9
Magus 6
Basic background:
They are at an outpost town bordering orcs / humans. Main forces are out of town, a red dragon has been extorting jewls from the town for months. Recently the PCs found a bronze dragon being taking down the road by some rocs. Turns out the orcs captured the bronze dragon after hired human mercanries tricked the dragon into helping save them from the red dragon. They tried to capture the red dragon, but it got away. The party freed the bronze dragon and now plans to go after the red dragon with the help of the bronze dragon.
They are at a town now prepping for this, so they have mercenaries and soldiers at their disposal for NPCs to go with the bronze draong, and they have access to a few special salves that can protect people from 1-2 dragon's breaths.
The bronze dragon is young, I haven't decided on what the red dragon should be, and luckily for me, they've failed all checks to figure it out and think he's somewhere between adult and ancient.
Just looking for some opinions on what CR/Age to make the red dragon and any other tips for this encounter.
I'd probably say go for a young adult (CR 13) or adult (CR 14) red dragon. A young bronze dragon is CR 9, which means you are effectively adding a level 9 to the party. That puts your APL at 10, so a CR 13 or 14 monster is still a significant challenge, even with a good healer and some protection from breath weapons.
Note that you should use hit and run tactics if the Dragon decides to attack the attacking PC's and using an adult dragon (Cr14 would be a good idea) Note that due to the action economy using just one BBEG is never the way to go in my experience (especially with 5+ party members). Throw in some orc barbarians or brute rogues to help the dragon when the PC's finally do attack (maybe even a curve ball with a half orc wizard or sorcerer). The dragon should have no trouble attracting the orc's help though either fear or promise of a share of his vast treasure hoard. The level for the helpers should be between 6-9. Sounds like an epic encounter to me.
Hope this helps.
To milk the most of this, I'd have two encounters.
1. Where the red attacks the town or wherever the PC's are camped out. Basically the dragon should do a ton of damage, particurlarly collateral and make full use of it's flight and breath,and optionally crush maneuvers. The PC's objective in this encounter is not to win, but survive and protect as many townspeople as possible. IF your players are new to dragons, this is a good way to demonstrate all the various ways a dragon can kill as it racks up a bodycount among the townsfolk.
2. The lair. This is where the PC's beard the lion at it's den, catching it in a place where it's mobility is a bit more restrictive. The first encounter should be instructive on how the pc's prepare for the second.
1) That's a fantastic idea. The town is an outpost town and under siege on a regular basis and has military units and civilians. Will have to do some map work for prep, but sounds fun. To add to it the dragon should be more pissed off than normal as an extra planar trader looted his hoard, so a raid on the town makes sense.
Also as pipedreamsam mentioned one bbeg vs a few more. I think the dragon will be smart enough to attack the town when its already being seiged by an orc raiding party.
As for the CR, im thinking that the adult will be the best way to go as it will have the fear aura etc. When the pc's do encounter #2 they will be fully prepared and probably hire a few mercenaries from the local guild (who they had contact with recently after they found a work notice for a hit on the party :)).
Thanks for the great ideas everyone.