GLABREZU - immune to my traps?

Theres a Glabrezu that spawns in the Guarded Compound in the Temple District, and it simply doesnt trigger any of my normal traps or spike trap. Is this normal? Are there traps (HLA) that affect them?
0
Comments
Well, the thief traps don't trigger on them. Indiscriminate spell traps (Skull Trap, Glyph of Warding, Delayed Blast Fireball) do.
Summoned demons, despite having that red circle and being hostile to everyone, are in the "allied" group. That's what the internal name "GOODBUTRED" for their allegiance means. And traps only trigger on creatures with allegiance in the "enemy" group.
however: in that place where the Glabrezu is summoned, there are also quite a few other monsters - i believe, also summoned, and they do trigger my traps: a Nishru, an Efreeti, some ogres, and more.
That trigger casts four mage spells at once, as if the mage you talked to when you entered had cast them. Summon Nishruu, Summon Fiend (the glabrezu), Summon Efreeti, and Monster Summoning 3 (one or two creatures, randomly chosen between ettercap and ogre berserker).
Incidentally, the name of the trigger in the area file is "Backstab" and its script is KETTAATK; presumably, that was meant to be the thief of their group surprising you with a backstab before most of the area's content got scrapped. So they threw together a magical surprise instead, and ended up with a mess that basically solves itself if you stand back. After all, the normal summons and the demon are hostile to each other...