Pathfinder 1E The Fools!

[7heprofessor]

tl;dr Need epic dragon battle feat, spell, and tactic suggestions.
I am currently running a Pathfinder game (with some 3.X content allowed) and the PCs have just reached 10th level by defeating my Fire Giant Jarl and his gnoll minions. The battle took place in one of the previously-floating castles that crashed to the ground on Faerun many years ago to create the Stonelands. It was unbearably hot in the keep without protective magics and once the giant was dead, the party sought the source of said heat. Through divinations and some lucky knowledge history rolls they were able ascertain that taking residence in the lowest level of the keep is an adult red dragon trying to unearth the Heartstone that made the castle float.
Now, I don't know if they're high or what, but they seem convinced that they have to go fight it. So we spent last session with them selling and buying loot and preparing for the battle. This next session will be them delving into the scorching hot dungeon level to confront the beast.
The party's composition is as follows:
Gnome Archivist Bard 10 (weilds a Dragon Staff and makes judicious use of Illusions and Pilfering Hand)
Half-Elf Archer Ranger 10 (with a Boon companion tiger and a frost bow)
Human Invulnerable Rager Barbarian 10 (supersition and other magic-hating rage powers)
Dhampir Summoner 10 (uses a defense-optimized biped eidolon with AC32)
Gnome Teleportation School Conjurer 6/Paragnostic Scholar 4 (makes average use of summons, very teleporty)
Aasimar (afflicted Werewolf) Cleric 6/Moon Guardian 4
With 6 PCs that puts their average party level to 11. An "Epic" encounter is equal to APL+3, or CR 14. An adult Red Dragon happens to be CR14!
So, my goal? Make this fight EPIC!
To do so, I have adjusted Seryndalar's feats (that's the dragon's name, FYI) and I would like your opinions and suggestions.
Original Feats:
Cleave, Greater Vital Strike, Improved Initiative, Improved Iron Will, Improved Vital Strike, Iron Will, Multiattack, Power Attack, Vital Strike
New Feats:
1. Iron Will
3. Power Attack
5. Hover
7. Improved Iron Will
9. Snatch
11. Multiattack
13. Flyby Attack
15. Quicken Spell-like ability: Pyrotechnics
17. Dazing Assault
I also have a few ideas about his lair. First of all, his goal is to excavate the lowest dungeon level in an attempt to find an artifact and the easiest way he knows how is to melt the floor away. This has caused pools of magma to form all over the place. He has been digging for some time now and the floor-to-ceiling height is about 200 ft. which should allow him to maneuver effectively aerially. He has dug ledges out of the walls for him to lounge upon and has treasure on each one.
The PCs will be entering through a tunnel at ground-level and have the vast lair before them with pocks in the ground spewing magma about and choking smoke impairing vision in multiple locations.
My idea is to use Quickened Pyrotechnics to blind the party and then Flyby Attack with Snatch to bite and grab one PC per round and drop them into lava. With Dazing Assault they will be Dazed and unable to get out of the lava for one round dealing 20D6 and then 10D6 for 1d3 rounds. This should remove their Protection from Energy spells and allow the Breath Weapon to actually do some damage. Then, Seryndalar will hide in the pools of lava and pop out and breath on them. Finally, he will Haste himself and fly 10 ft. above the party and full-attack them to death with Dazing Assault.
One final point: this battle has nothing to do with the story so I feel no remorse killing them. I am not a vindictive DM and never purposefully kill PCs, but they are walking into a dragon lair and hope to kill a dragon for its loot. IT'S GONNA BE HARD!
Suggestions/comments/questions?

 

[DnD_Dad]

My favorite dragon tactic is, if the party is fighting in a dragon's lair(treasure & magic items) then the dragon flaps its mighty wings a causes hundreds of coins, magic weapons, etc flying through the air at the party. I also include this as a free action as a dragon can fly as it mode of travel and only has to grab hold of something with its hind legs to stay put while doing so.

 

[sheadunne]

Action economy is going to kill the dragon. For each turn the dragon gets, the players get 6+. A skilled party will have little trouble with the dragon. If you really want to make the fight interesting, give the dragon young dragons or elementals to also contend with. Single baddie fights tend to end in 1 or 2 rounds, maybe 3 if no one memorized dispel magic. A single illusion wall over the floor will prevent the dragon from fleeing (assuming it fails its will save). A wall of force would work nicely as well. My usual gaming group would have little issue with the dragon. Your group may be different and not as tactically motivated. It's not that the dragon isn't difficult, it's just that it gets only one turn a round. Balance the number of actions and the fight will challenging.

 

[Stormonu]

I've found overrun and grapple to be extremely deadly with dragons, moreso than Breath Weapons. Overrun/bull rush opponents, grapple/snatch to carry them into the air and drop them from heights. Fly-by attack + Snatch can be quite deadly, as could Awesome blow into a pool of lava.

It looks like the party has lots of anti-spell abilities and would probably mow the dragon in straight-up hand-to-hand. I'd concentrate on spells that the dragon can cast on itself or on areas that don't require saves to work. Rock to Mud could be used to devastating effect in the battle to slide PCs into lava or turn solid ground into a quagmire that can fill with lava. Grease or other terrain-affecting spells (entangle, silence areas for the bard and spellcasters, web) could make standing or getting around for the PCs difficult, if not impossible, whilst the dragon just flies overhead.

Wall spells can be used to isolate PCs or funnel their movement options, including allowing the dragon to take on PCs one at a time. I believe both spells I mentioned could be used without breaking invisibility (or just use Improved Invisible).

Dropped/thrown boulders or stalagtites or other large objects (including hurled magma) could be used as ranged weapons by the dragon so it doesn't have to close to melee except to polish off the PCs.

 

[Razjah]

I would consider letting the dragon act on multiple turns. Say N and N-10 for Initiative, which will help out with the action economy issues.

Slaves or some minions could be useful to a digging dragon (that is work for plebs not great dragons). You could include loads of scaffolding as the area has been dug out, which could allow the dragon to collapse the terrain the PCs are fighting on.

Perhaps have some giant stalactites that the dragon turned into a temporary lair. It could have delved out sections of these giant stalactites that allow it to fly/crawl through sections of the ceiling. Those could have collapsible sections if the party pursues the dragon through them.

 

[Herobizkit]

I would suggest running the fight as a Boss Battle. It's a "system" I've read on The Angry DM blog. It's based on 4e rules, but I think it could apply very easily to PF.

http://angrydm.com/2010/08/the-dd-boss-fight-part-4/

In short, your boss would have three "stages" of fighting, each spaced across 1/3 of HP total. After each "stage" is defeated, a special effect occurs to disengage the monster, bring it back to "full" HP and have it attack with new tactics. I'd say throw in some dynamic battle areas as well - Have the floor slowly break away with lava beneath, fr'ex, or a portal that generates small but frequent elementals every round, or (if you're feeling particularly mean) have a pair of Pyrohydras to help whittle away their fire resistance (or be really mean and put in Cryohydras...)

 

[ggeilman]

Well unless it is an awefully big lair, most dragons are better off fighting out in the open rather than in their lair. It takes away from them being able to do flyby attacks. 6 11th level PC's should easily be able to handle an adult. I would make it a a mature adult at least and give them a little more of a challenge. Either that of give it a lot of guards for its lair. Your choice of feats are good though. You might look at Dragonlance 3.5 for ideas on dragons also. At 11th level I was throwing advanced blacks and blues at the party!
I have had an adult red dogging the party since 3rd level and is now harrassing them at 6th. Yeah, I am mean!