Have a problem with speed, dx is lowered

Im new in this post but ive been playing arcanum for 3 years, but never encountered this problem.
I went down to tarant sewers -the one which was closed- i killed all the creatures down there, but when i got out of there my speed was lowered. I was like walking. So i opened the vhar window and dex was lowered to 1. Can you help me? There doesn't seem to be any injury or curse in the journal.

 

You have picked up the Blackstone Blade, I fear. It is a cursed sword that gives you a permanent -4 DX when you equip it. There is no way to lift the curse, unfortunately, so I hope you were saved before you picked the blade up.

NEVER equip yourself or your followers with magick items that have not been identified, unless they come from a "legit" place like a magic shop or a quest reward. Also keep in mind that your followers will automatically equip themselves with any weapon in their inventory that they find more powerful than what is already in their hands, so watch them closely when you give them unidentified stuff.

 

Except for that Medallion you get for killing the beast roaming the colony in the Isle of Despair.

 

It happend to me too , lucky as i am , i had a earlier save game