Board Thread:Warhammer 40k General Discussion/@comment-91.224.27.226-20131031140001/@comment-3258762-20140105233832

Vaughn891 wrote: I mean I think they left them blank for situation involving Chapters Like the Blood Ravens whose Primarchs unknown. Some think its Sanguinus others think its Corax for all we know it could be one of the missing two. The most accepted "canon" for the Blood Ravens are that they're derived from Thousand Sons Gene-Seed. The reason the two are left blank, as has been said here and officially stated by Games Workshop themselves, is to allow you to build a backstory for your own Primarch.