Board Thread:Warhammer 40k General Discussion/@comment-4851119-20140118095944/@comment-24383134-20140201010717

The two lost Primarchs are imprisoned in the labyriths under the Imperial Palace.

The lost legions were folded into the Ultramarines, but their geneseed was kept seperate by order of the Emperor/High Lords of Terra until a later Founding when they were dispersed as a 'new' Chapter.