Well... I'm a Heavvenly Official so 'dealing with ghosts' is sort of my job...

But this Lord Ahra is at the very least a Wrath-level ghost with how he can keep the army in its thrall. I have a feeling that if we managed to make him pass on or destroy him, the rest will probably dissipate as he'd be the one keeping them here.

If he won't listen to any reason, and nothing else works to appease him, then destroying his bones and ashes would be a last resort, but we'd need to find them.