Unique: Slayer's Blade
"Have fun."
Damage: 5d4
Accuracy: auto-hit, 100%
Unmoddable.
If you have the Slayer's Blade in your equipped slot (or prepared slot with MMB), you cannot berserk. At all. Berserk packs won't work, Berserker won't proc and if you're berserked when you pick the SB up, you calm down.
However, whenever you score a hit on an enemy, you get a +1 to melee ToDam. This accumulates, so you may very well be dealing 5d4+30 when you're fighting the Angel of Death.
Every three actions you take that do not involve hitting an enemy or being hit in melee by an enemy, you lose one melee ToDam (does not drain any melee damage boost from Brute).
As an added bonus, whenever you have a ToDam bonus that is above 20, you will leave pools of blood wherever you walk.