Watcher's Keep final seal: question about setting traps

FredN

.....OK,continuing my all evil run, I am in the very bowels of the Watcher's Keep. The Helmitic Ghost said "great job! Here's a key! "
.....OK, I'm no fool; I knew that when I started fiddling with the seals, all Hell would (literally) break loose. My thief is Hexxat, who, at level 28, has a 110 set traps skill and can set 6 spike traps and 2 explosive traps per day, for absurd amounts of damage. So, I had her set all 8 traps in various areas around the seals.
.....Then I triggered the first wave of defenders. They were led by some loser whose name I forget but it began with an A; I won't go into a blow by blow desrciption of the fight, but it took forever to take him down. However; this isn't relevant to my question. We won the battle, but not a single one of Hexxat's traps ever were triggered. I had no clue why.
.....Having won the battle, I wanted to know what was going wrong with Hexxat's traps, so I reran the scenario several times. I put traps in the spawning areas, with no effect. I tried again, and put the traps further away, and tried to lure the foe into the trapped areas. No traps went off. Now, if the developers didn't want traps to be effective in this area, they should have given a message that the trap setting failed. But Hexxat always gave her standard trap success message "someone is in for a surptise".
..... I have no clue what the problem may be; I did consider that maybe all these enemies spawn with true sight in effect, which would let them avoid the traps. But I'd really like to know, just for general information purposes, whet the heck is actually going on here. Thanks for the input ...

FredN

OK, never mind the question. I just finished the globe machine part of the seal quest, and Hexxat's traps worked just fine there. I susoect that the flaming skulls from the first seal didn't trigger any traps because they were floating in the air, and thus didn't actually step on any of them. A bit odd, but understandable.

jmerry

The flaming skull enemies should trigger sufficiently close traps; there's no actual "floating" mechanic in the game. They do have the ability to see through invisibility (and also can't be backstabbed), but that doesn't help them avoid traps. They're also immune to fire, so any explosive traps would be useless. Actually, they're over-immune so fire damage heals them slightly.

The one you have to watch out for is the Rilmani. They're immune to magic damage, so spike traps are completely useless in that fight.

FredN

Fire heals them?? Ick! I had laid down two explosive traps and a delayed blast fireball from Edwin. No wonder there was zero effect on them. I had no idea about that being the case.