I was flipping through the various pages of Codex: Blood Angels fluff today and came accross a Necron encounter, being a Necron player I read the short entry and it went something like this:
Blood Angels (inc Dante) meet a force of Necrons (led by a named Necron Lord that I can't seem to remember) on a planet and start fighting, 3 weeks later neither side is winning and Dante is giving it everything he's got. Suddenly a Tyranid fleet arrives in orbit and lands planetside where the Necrons and Blood Angels quickly team up to combat the new foe. The alliance of Blood Angels and the Necrons s enough to annihilate the Tyranids and afterwards the commanders go their seperate ways, the blood angels believe it to be dishonourable to turn on the force they just fought alongside with to halt the Tyranids and both sides had sustained casualties. wtf?
So for some reason the Necron Lord worked with the BA's, Dante willingly accepted their aid, and afterwards they thought it was more important to be honorable and leave the Necrons alone because they fought alongside them in battle, and it never mentions them even returning to combat the Necrons again.
It also struck me as rather odd that the Lord would go along with this, he worked alongside he BA's and even at the end, where he probably should have continued to harvest the BA's, he lets them leave!
The whole sory seems kind of odd and it is the first Necron alliance i've heard of..... any thoughts?