Trolls Inexplicably Immune to Mind Spells

[AskRyze]

Description of Bug Experienced:
For some reason, a number of monsters in the module seem unexpectedly immune to mind affecting spells despite failing their saving throws, with no explanation as to why in the combat log.

Steps to reproduce the Bug:
Cast Mind-Affecting spell at Troll, Troll fails saving throw

Expected Result:
Troll is affected by mind-affecting spell

Actual Result:
Troll carries on its day with narry a care in the world.

Screenshot(s)

There is no feedback text in the combat log to suggest mind immunity/paralysis immunity / manipulation immunity from the ice troll.

Additional Information/Notes
I have replicated this with both Troll Plague-Bearers in the Slime Temple and with the Frost Trolls on the Ice Road. Both trolls are still able to fail saves vs Slow and other non-Mind spells. I do not know if this is affecting other mobs but if I come across it further I will update this post.

[Xerah]

This happens if they haven’t been damaged by fire or acid yet.

[chris a gogo]

Trolls have always been immune to mind effects.

[AskRyze]

This happens if they haven’t been damaged by fire or acid yet.

Trolls have always been immune to mind effects.

In most cases, if a target is immune to mind spells, there is a combat log popup in bright yellow text that states "Target is immune to manipulation". Why is there no prompt in this case?

[cornelius_4]

While just a guess, it might be a kind of custom implementation (like not giving them immunities in a standard way, but scripting immunity to some things).

It's an old system - it's always been a little off, that they have been immune to stun, hold, mind and death effects too (I think), before having taken 1+ points of acid/fire damage. But the coolness of having the fire and acid interactions well outweighs the incorrect immunities (imo).

Also, once you know how it works, it's fairly managable to pack some acid splash scrolls or an acid/fire essence. Though if it were possible to have fire/acid interaction witout the quirks, it might be just a smidgen better.

I've developed a habit of hoarding a stack of acid scrolls just for this, even though I don't seem to need them as much as I used to. They often get to 70-80 scrolls, apparantly must be thinking "Someday... there will come a time when I will need to mow down ALL the trolls and my other means of burning them down shall not suffice and then THIS will come in handy. Heh.