Hijinks in Schloss Caromarc

[Ermehtar]

So, an interesting thing happened the other session while my group was in the Schloss in Book 2. Spoilered to prevent unintentional reveals.

Trap fighting trap:

So, my PCs were able to figure out the gambit with the guard's uniform and used it to bypass the flesh hound on the bridge, the trap on the main door, and the Hook-hand Apparatus. They did trigger the Erinyes trap, however. Being saavy adventurers, they high-tailed it when they saw a fairly high-level demon appear before them. They knew they just had to wait her out, as she was a summoned creature. So they fled back into the main house. The paladin bought them enough time with a smite and some LoH before falling back, too. I decided that the erinyes, being summoned to destroy them and irritated with a paladin of Iomedae, followed them. She started tossing unholy blights through windows, and the PCs ran desperately to seal themselves into an interior room.

She followed them around, still tossing spells through windows, until eventually they sealed themselves off and the erinyes was on the front side... with two doors... one MUCH closer to her prey... and she wouldn't know about the traps or anything.

The erinyes, not wearing a guard uniform, triggered the air elemental trap AND awakened the Apparatus when she broke down the door. She was easily able to fly away from the Apparatus and beat the holy living hell out of that elemental but her duration ran out and she vanished.

Needless to say, my players were highly entertained by the way it turned out, and I must admit I laughed, too. Has anyone else had this happen, or did I just run this encounter wrong?

[Rubber Ducky guy]

I'd say you ran the encounter right.
You asked yourself "What would this monster do?" and then acted on it in a natural way.

The result was a cool story you and your players will remember for some time.