Battle of Maedrax
After Farseer Eldrad Ulthran foresaw an Imperial Explorator Fleet awakening Necrons entombed on Maedrax, he has the forces of Ulthwe quickly move through the Webway and ambush the human ships. The Eldar then make planetfall in force and attempt to purge the Necron presence before it can awaken. However a Battle Barge of the Blood Angels soon arrives, exacting a heavy toll on the Eldar. Worse still, the Necron presence is much higher then originally believed and an entire Dynasty awakens and overruns the system.