Syndriiq's Sump?

In the Coven Supplement, the Syndriq's Sump relic allows the bearer to choose Poison (4+) each turn as one of the abilities.  This seems kind of odd since the entire army pretty much has Poison attacks already.   It also doesn't say if it applies to the bearer's shooting attacks or close combat attacks, so I am wondering if I purchase it for Urien Rakharth, would this makes his Casket of Flensing a Poison (4+) AP 3 shooting attack?

Urien cannot take any additional wargear as per his entry in the codex dark eldar i believe.
For every normal haemonculus though, i think you've raised a very solid point that i haven't seen mentioned before.
Could be interesting!

Oh, yeah, I just realized Urien can't take any artefacts or relics.  

But as you point out, for  a Haemonculus, I don't see why this wouldn't work.  It may actually make purchasing a Liquifier for a Haemonculus a worthwhile investment.  

Be interested to hear other's thoughts on this.

I really, really want this to work, but I don't think it does. The wording of the Poisoned rule is that if it's on the model, it's just for melee attacks, and needs to be on the weapon for shooting attacks.

Dammit.  I just re-read the Poisoned rule and you're right.  Sigh.  Oh well, I'll always have those brief couple of hours when I totally thought I figured out a way to make Liquifiers worth taking.