How stop the dark eldar when they are in T3?

someone know as win the dark eldar when they are in T3 with necron?

The Warp Beasts are very strong units and the big ship is very very very strong. It's impossible stop with necron.

Someone can help me?

Thanks

If you know any replay, you tell me it

Knowing DE and having played as them quite a lot, I would recommend that you send off the Lord at their base, transform him into nightbringer, while teleporting plenty of FOs, which should knock out the Warp Beasts (Morale loss), while the C'Tan can deal with the D of D, and while that's happening, have your monolith teleport as close as possible, making lots of new, and free, necron warrior units.
Alternate method is to position the Monolith as close as possible, send in the Lord and transform into deceiver, and summon another Monolith, and then teleport the real Monolith in, teleporting as many squads of Warriors there as possible. Also make sure the Lord has the Res Orb, and also that your base is well protected.
Your choice of vehicle in both cases should be 4 D, and 2 HD, and a TS.