[ThaVirus]

They mention it briefly. I'll put the following in spoiler tags but it really doesn't spoil the story much..

Spoiler!

They have a brief montage of scenes of him with the Necromongers. He's been drinking and ****ing bitches- basically neglecting his duties as Lord Marshall- all the while thwarting assassination attempts by Necro generals.

He says he was becoming too civilized and needs to find the animal side again so eventually he asks Vaako where Furya is located (since he's apparently the only one in the universe that still knows where it is). They end up on the planet where Riddick III is set, which is not Furya, where some douchey general attempts to assassinate Riddick and leaves him for dead on the planet.

The douchey general shouts out "You keep what you kill" so we're left to assume that either he or Vaako would now take over as Lord Marshal. If they plan on continuing the series, I'd imagine Riddick will have to confront Vaako once again to find out the true location of Furya. Or perhaps they could have that Shirah spirit chick visit him and reveal it's location.

That's all I can remember of them mentioning the Necros.