There's code in the python spell req. for Resurrection that's supposed to keep that from happening with Korrina. Isn't working for me, either. Could have sworn it worked in FF.
A little more on this: The code is supposed to check and see if there's greater-than-zero number of Korrina's around. Setting it to equal-or-greater-than-zero does turn off the spell. So it looks like the unitclasscount isn't working, though I've no idea why.
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Haunted Lands Spread:
I've realized there's a least one significant flaw in the current system: The more land you have the quicker you get Haunted Lands. One Ghost Walker in a Scions territory of 100 squares will have 10x the effect as a Ghost Walker in a Scions territory of 10 squares.
Furthermore, I think the current system is boring boring boring. No micromanagement, which was supposed to be the point. But very boring.
I've got an idea with no real micromanagement: Give Ghostwalkers and other Haunted Lands-ish units a small per/turn chance to spawn an AI controlled Creeper. The Creeper would be set to Explore and self-destruct or plant a Haunted Lands feature within a few turns. (Maybe even outside Scion territory if you're already at war.) So you park Ghostwalkers where you want HL to spread and it'll do so in a vaguely organic manner. (And there's no "more land = more HL" problem.)
The possible problem I see is the pathfinding for the AI units. There shouldn't ever be all that many of them, but I don't know how many would be too-many to significantly hit turn speed.
A variant would be even fewer, but non-AI controlled Creepers with a few more abilities. But no Creeper aging or stockpiling.
Another possibility: Auto-castable Ghostwalker spell. (Basically the original method in FF, but taking advantage of WM's autocast.)