Word Bearers, Kronus Liberators and Blood Ravens, all are driven to the earth by Ulthwe.
Assaulting Deimos peninsula was superb fun and the hardest fight so far. I love how varied the objectives in the fortress assault levels can be. Especially the Deimos peninsule fight were you had to first get rid of the blood pulse pillars by taking hold of the Khorne point there. If that wasn't difficult enough, the enemy outnumbered you three to one and Chaos Lord Eliphas ascended to demonhood halfway through the level and started pestering you all over the level, flying and assaulting your forces from the air. Then there were bonus objectives and such, Throughly an enjoyable experience. The debriefing was also great: I could just imagine the kilometer high runes of light the Eldar used to cleanse the peninsula.
Granted, the Victory Bay fight against the Imperial Guard was a bit better, what with the Titan Hellstorm cannon blocking your way(and killing all of my Warp Spiders on the first meeting) and with the basilisks bombarding your poor troops advancing through the mishmash of mines, turrets, tanks and rows upon rows of soldiers. Yes, and four Baneblades. :D
Too bad that the Eldar are rather useless against Necrons, especially ones with a full honour guard. I don't plan on attacking them in their stronghold(army strength 14 there plus the honour guard is there) anywhen soon. They really are the biggest threat in Kronus.