via a solid source here on Faeit 212
I good an answer about that "auxillary set" from one of the last rumors.
It's a set with different weapon options (in the same fashion like for Necromunda and those close weapon sets from FW) which couldn't fit into the regulary Horus Heresy sprues.
PREVIOUSLY ON FAEIT 212
This bit refers to a previous rumor found at the following link on a Space Marine Auxillary release.
