Ok, LotIF continued...
Our DM saw the problem with Blasphemy and the 3.5 pit fiend. As LotIF is written for 3.0, he took the 3.0 pit fiend, changed its DR to 3.5 but left its caster level (17), spell selection and powers as they are in 3.0.
Nevertheless, the party was badly beaten and forced to retreat via Teleport when cornered by the boss, the pit fiend and a fallen trumpet archon. We fled to a secret cave and prepared directly our next ambush with better preparation. Our cleric of Kelemvor regained his spells in the evening, as well as our wizards, after resting the rest of the day. The druid was still ready for combat with some buff spells for wild shape. During the night, we returned to the fortress. One of the wizards located the boss with Locate Creature. Again, we went through the wall with a Glove of Rust and assaulted the boss (who was unguarded at that moment). The paladin killed him like a lousy dog, when the wizards had dispelled all the boss' protections. The fiend and the archon showed up. The archon was dealt quickly, the fiend was very though. But a Dimensional Anchor from the cleric prevented nasty teleports, and after a hard fight (with weapons unable to beat the fiend's DR and regeneration) we finally managed to kill the fiend with a rope around its neck.
Thanks for the comments so far.
