My Dark elven Beastfighter was on 20 strength but shadow troll and regular shadow(black "G") took me 2 points of strength to 18. But with kicking stairs, just as in fortune cookie info, gave back 2 points of strength. Just was kicking stairs 2-4 times when entered a location. But I was below 11-th level.
I know the long time kicking stairs will result in level collapse. Maybe one kick at stairs won't be so bad.