Now I've tried a couple of times to have my strength drained by spirit trolls, and it seems that although my stregth stat returns to normal, the thac0 doesn't. My main character has suddenly gone from base thac0 12 to 18 after the fight against Tor'Gal and his minions. Shouldn't it return to normal after the drain effect wears off? Has anyone else tried this? It's quite annoying, but I'm thinking of fixing it with SK. Just wondering if it's because of a bug in a mod. I'm particularly suspecting Tactics, because of the troll upgrade.

Cast restoration and rest... if that fails try setting str with a belt of giant strength. If all else fails do SK or reload...

Hmm sounds like a bug. Are you blinded? Do you have any nasty effects? Cast restoration, dispel magic etc. and rest. If this fails; you have the right to SK. Have you been victim to Holy Smite or Unholy thing? They were buggy AFAIK, they leave permanent damage on a failed save vs spells.

No effects or blindness or ability drain. I've tried casting restoration and dispel magic. I think it's time for SK.

I'm not sure what caused it. It was either the standard attacks of spirit trolls or Unholy Blight. Guess I'll just have to see if it's repeated when I go to the druid grove.

Try Heal, too. I haven't noticed my THAC0 go down when hit by those trolls, but I don't have Tactics, either.

Thac0 can't be drained directly. It must be strength or level. Unless it's a bug or someone has cast a long-lasting bad spell on you. I remember unexplained thac0 problems in my own games, but they didn't really last for long. Tried resting?

@chev:
See 'Soul Reaver' (item code SW2H08)
Combat Abilities: Each hit makes the target receive a cumulative 2 point penalty to their THAC0
Duration: 20 rounds If that effect was cheesed onto the spirit trolls via Tactics (with a duration of permanent instead of 120), then you should avoid getting hit. ;) Or just try every status spell you've got.

I've tried a couple of other things now. Tried casting heal and remove curse. I've tried resting several days. Keldorn has also been drained so I killed him and raised him. Nothing works. :(

I've Tactics myself and resently i fought Torgal and got str drained, but my tach0 is just fine, perhaps as you say it it may be a bug...