Board Thread:Warhammer 40k General Discussion/@comment-4851119-20140118095944/@comment-25073042-20140617073257

Bumping up an old thread, but I found this:

The sunken chambers of the galleries are crowded with artefacts of all forms: the fabled Wraithbone choir of the Eldar Altansar Craftworld, the preserved head of Sebastian Thor, the ossified husk of an Enslaver, and a giant of a man clad in baroque Power Armour, his face contorted in a permanent scream

source: http://warhammer40k.wikia.com/wiki/Trazyn

If that giant guy ain't one of the missing primarchs, I don't know what is :)