The first time I tried that quest, the terrors ate my lunch too. So after a resurrection, my mage, being of high intellect and enjoying doing research and stuff, decided to see if there was some documented weakness those terrors had. He stared into his crystal ball (internet) and discovered that yes, not only they did have one major weakness, but someone had already figured out an entire strategy for not just getting past the terrors, but doing that whole verhoffin ruins book quest at the beginning of the game! (speed game version)While speed games are too tedious for my taste, the weakness of the terrors was something I exploit every time I play now (otherwise I'd have to be a level 100 scholar first). You see --- they CANNOT open doors. So all you really have to do is run really fast. And if you go into turn-based mode carefully, like strategy suggests, you can grab that key (or whatever it is) on the table and slam the door in the beastie's face before she gets her turn. It's true there's another terror in your way, but all you have to do is beat her to the door, go turn-based, open it, and slam it shut and then exit turn-based.
If you want the whole strategy, I think it's at Ribannah's site in her speed game (if I'm mistaken and crediting the wrong person, someone please correct this).