[Eberron]Need to amp up an Elemental (WoE stay out!)

[Reynard]

I am running an Eberron campaign with five 13th level PCs, and I need to make a Fire Elemental into a credible threat.

The basics: The elemental is bound into the Khyber shard of a downed airship. The PCs will come into conflict with agents of the Emerald Claw in trying to retrieve the shard, but no one knows the elemental in the shard has gone Maaaaddddd from being trapped within for years. The shard is also cracked, so the elemental can attack but not get out. Should it get released somehow, it will go on a rampage.


I thought about giving it a template, but I couldn't find one that fit. I also thought about 'gestalting' it with an Efreet -- i.e. giving it the best of the two monsters' stats. How much do you think this would increase the CR, if I were to do such a thing? What other options -- other than just advancing it with HD -- might work?

Thanks.

 

[Ferrix]

Elder Fire Elemental CR 11

You could give it the Corrupted template which could add some spice to the encounter, even though technically the corrupted template can't be added to outsiders, who cares.

It would gain:
+8 natural armor
Natural attacks increase by one category (2d8 becomes 4d6)
Disruptive Attack: Deals 12 vile damage with each hit.
Enhanced Power: +4 to the DC's of all of it's powers
Fast Healing: 10
Str +4, Dex -2, Con +4, Wis -2, Cha -2
CR +3

Combining it with Efreet sounds interesting, I'd imagine bumping it's CR by 3 or so.