R.A. Salvatore fans: Stat Charon's Claw!

[aco175]

The books talk about it being one of the sharpest blades around, so +3. I would also just make the ash ability impose disadvantage on the next attack to keep it simple.

 

[Alzrius]

As the

EDIT: Well, this one lists pretty good the abilities presented in the books: http://forgottenrealms.wikia.com/wiki/Charon's_claw

That article notes that the sword was written up in Dragon #359 (p. 58), for D&D 3.5. It's a fairly short entry, but manages to cover the basics:

CHARON'S CLAW
Minor artifact
This is a +4 keen smoking longsword. Charon's Claw is powerful blade of Netherese origin. Possessed of a powerful and malign intelligence, potentially a bound fiend, the sword is capable of disintegrating any wielder it deems unworthy, unless the potential wielder succeeds at a DC 25 Will save. Additionally, the sword possesses a number of unknown, quasi-magical abilities that remain dormant unless within the area of a Netherese mythallar.