Overpowered weapon mod? Souldrinking from 3.0 book

[Xexyz]

I'm thinking of giving the BBEG (a lvl 16 Antipaladin) in my campaign a sword with the Souldrinking mod from the 3.0 Book of Vile Darkness. Souldrinker bestows a [temporary] negative level each time it inflicts damage with a hit; crits bestow two negative levels and give the wielder 1d8 temporary hit points and a +2 Str enchancement bonus for 1 hour. This attribute is worth a +4 bonus. Is this overpowered?

My other thought is the Marrowcrushing mod from the same book, which inflicts 1 point of Con damage with each hit (no extra on a crit). That mod is worth a +3 bonus.

Thoughts?

[kyrt-ryder]

Neither is particularly overpowered in and of themselves, but there are a million other factors to consider. Like with anything else, it's the combination of things that tend to break encounters.

[Blueluck]

I don't think either sounds too powerful.