My third game was vs Dark Eldar

I was running:
Mephiston
Assault squad with 2 meltaguns and sarge power fist
Assault squad with 2 flamers and sarge power fist
Devestator squad with 4 las cannons
Devestator squad with 4 plasma cannons
Baal predator with Inferno Cannon, Heavy Bolter sponsons and HK missile
Baal preadtor with Assault Cannon, Heavy Bolter sponsons and HK missile
Sanguinary Priest with Jumppack and power fist
Sanguinary Priest

My opponent was running:
Archon
Baron Sathonyx
Incubi
Kabalite warriors in a raider
2 units of Kabalite Warriors
Wyches
Helions
Beastmasters with Razorwings, Khymarae
Scouges
2 ravagers

The game was spearhead and 'dusk' - night fighting rules starting on turn 5.

My opponent stole the initiative, planted a webway portal, and proceeded to swamp me with troops.

My assault squads and mephiston counter attacked, making good accounts of themselves, but I never fully recovered from the initial assault.

I made use of my Baal predator to escort the Baron off the table after my assault squads wiped out the Helions. In the end I was left with one Baal, and lost the mission 9 kill points to 8.