Fuck em they're elves. At this point your best bet is to just kill more eldar, and while your at it hoard the soul stones of your victims. That way when once the dumb bastards finally back you into a corner you can trade the sweeet sweet eldar souls for some kind of bitchin slaaneshi pact! There'll be cocaine and motorcycles for the whole crew! I mean sure you're still gonna die and slaanesh is going to smoke your soul, but it'll be a death your group will never forget!