There is some information coming in now on the new Dark Eldar Coven supplement that is part of the Archon limited edition and coming up here for pre-orders. Of course this is still very early information, but if you are planning on running Wracks, Talos, or Grotesques', this looks like the way to go.
Please take these as rumors, until we get the official release. there is a lot of room for error until release day. I removed point costs etc, from this bit.
via Shite Dwarf
http://shitedwarf.blogspot.co.uk/
COVEN Supplement
Power from pain - by turn number.
1 – nothing
2 – Fearless
3 – Fear, Fearless
4 – Fear, Fearless, it will not die
5 – Fear, It will not die, zealot
6+ - Eternal Warrior, fear, it will not die, zealot
Warlord chart
-talos & chronos reroll FNP rolls of 1 within 12”of warlord
– warlord plus any grotesques he joins gain it will not die
– add or subtract 1 from reserve rolls
– If your warlord is slain by an attack/weapon with AP 1 or 2 or with the ID rule, gain D3 VP
– Warlord plus wracks he joins gain FNP4+
– Warlord gains preferred enemy
Artifacts – pick one of the following at the start of your turn which lasts until your next turn – IWND, fleet, poisoned 4+, rampage (used each turn)
fighting in a challenge – opponent suffers -5 to initiative
-8”range, S1, AP2, assault 1, blast, instant death, no effect on vehicles (used as a grenade in shooting phase)
-Additional D6 attacks at S3, AP- at initiative 10, grant an additional pile in move at this step, no bonus applicable for furious charge, rending etc
-IWND 4+, only wounded by poisons special rule on 6
-+1 to FNP rolls, negate first wound suffered if it has the ID rule but when this happens, the item is lost
Coven Detachment Required – 2HQ, 2 Elite
Optional – 4HQ, 6 Elite, 4 Heavy Support
Units that are available in the detachment – Urien, Haemonculus, Raider (DT only), Venom (DT only), Wracks, grotesques, talos, chronos
Benefits – if this is the primary detachment you can reroll warlord chart from this book. All enemy units within 12”of 1 or more models from this detachment suffer -1LD
7(!!!) formations as well!"