I think the weapon is fine as is. I always do Nalia's Keep early in the game (day 10 or less). Thus, this weapon is used by my fighter/mage early on. This weapon is not a game breaker. Consider that the both the Strength drain and Slow are temporary. The strength loss is only 1 point and that assumes the enemy fails his saving throw. Most enemies have mid level strength (12-17). Thus, there is virtually no effect on combat until their strength drops quite low, say 3-6, when they start to get subtractions on THACO and damage. The monster is probably long dead by the time his strength gets that low. Slow is a weaker version of the flail of ages because it allows a saving throw. I don't solo, but I suspect your character is already casting slow in most battles. Finally, as far as the damage goes it is 2d6 not a flat 12 points of damage. The damage with the dagger is very comparable to that of a +2 long sword or the +3 battle axe found in the Keep. In short, this is a great weapon in the early to mid game until you find a replacement. Torgal's Claw is a good weapon but certainly not in the same league as the Staff of the Magi, Daystar +4 (from item upgrade) or Celestial Fury.