What do you think about this situation? An impostor efreeti seems unstoppable

[Jon_Dahl]

Two sessions ago my players faced a small fire-themed army that attempted to invade their home kingdom. It was a surprise attack out of nowhere. I had planned the attack very carefully but I was disappointed to see that the efreet are useless, at least in closed spaces. I noticed that they were easy to kill. I decided to fast forward the players to encounter the leader of the "fire army". This advanced 12HD efreeti with 4 levels of sorcerer (hence 16HD in total) had assumed the identity of a mercenary lieutenant after a battle that a platoon of the fire army had lost against a mercenary army. The efreeti was now leading said mercenary army away from the theater with the false pretense of recruiting more soldiers, even though he was just trying to get to the capital and assume a more useful identity.

The players recognized the leader through hints that I gave them. Then they decided... to flee. They faced the same efreeti again while it was traveling with its army to the capital. Again they fled. They haven't fought it at all. Now the efreeti is going to arrive at the capital and most likely assume the position of someone important, but not too important.

I don't understand my players. Of course the problem was that the efreeti was accompanied by an army, but if they know that someone is a shapeshifter, is it impossible to reveal that to everyone and then kill it?

The PCs are:
Dwarf Cleric 11 of Boccob (N)
Minotaur Barbarian 9 (CN)
Dwarf Expert 5/Horizon Walker 6 (N)

[FocusWolf413]

They didn't have any reason to think they'd survive. They discover the efreeti, attack it, then what? Get mobbed and murdered? What if they succeed in killing him? He's only temporarily stopped and certainly not permadead, but they certainly will be.

You put them in a lose lose situation and are confused why they're cutting their losses.

Once he's in a position of power, what next? Why would they know he's doing that? What realistic way could they ever find out he's an imposter? Why would it even be them? Why does it have to be super complicated?

[Mr Adventurer]

The Cleric can cast True Seeing (edit: and Banishment), so, in response to your question, no, it's not unstoppable.

[zlefin]

if they kill it first; then it assumes its true form so the mercs will realize they've been duped.
but that mgith be tricky, let's see, i'm sure there's some spells/ways to verify that the creature isn't what it's supposed to be. (ie spells that reveal it to everyone)
if the capital is the PCs sides' capital, they can just have a force meet the merc captain there and have the royal wizard/whatever try to declare it so; since the mercs are being paid by the kingdom they'd be more inclined to listen to such (if i'm reading the scenario correct).
who are the mercs aligned with/being paid by? since that affects a lot how much they'd listen to the PCs. but really, in any dnd world, i'd expect people to know about the risks of shapechangers infiltrating and have some countermasures. did you make disguise checks for the Efreet? it's skills at disguise aren't that high, and even with the circumstance bonus and its good stats, some of the mercs might spot irregularities. if the efreet is acting normal enough they might not get the opposed check; but the party simply declaring that it's an impostor would be enough for some of them to get an opposed check.

[Goaty14]

I'ld be pretty scared if I was level 9 and had to tank a level 4 Sorcerer Efreeti

HD 16 makes it huge btw

Not to mention the stack of its SLAs