Though cool I've noticed these tend not to grant immunity if the spell is cast just around the person they aren't immune to it at all, so unless it is cast directly on them, they aren't immune, and additionally its only the initial save, following that you are affected by the spell completely normally. I noticed this as I cast grease on the ground then walked into it which then I was totally affected :/ Or when i get something to summon a web spider and then i run into its web and am webbed.
Suggestion? Perhaps this can be fixed somehow? If not, then items with such immunities be altered slightly if possible. Relatively small thing, but i thought worth mentioning. Was not sure whether to add this to the bugs section or here.
I believe the spell immunity items are hard coded to only grant resistances to the spells. For example, there was a common item in EFU:A with Immunity: Web, and it did not protect against the spiders in the Webbed Woods, because their bolt attack is considered a "spell-like effect" by the NWN engine rather than a spell.
It is important to note that this also applies to Immunity: Flesh to Stone. It will not protect you from a petrification gaze attack!
Not talking about attacks with the spell-like effects, but rather the spells themseves as in the actual grease and web spell, they aren't protecting against the spells.
You're immune to the primary effect (slow) but you'll still need to make the saves for the side effects (falling in grease, getting stuck in webs)
I'm pretty sure this is hardcoded, like the above said.