User blog comment:BioChimes/Whisper Dragons in the firing line?/@comment-33731050-20140617224302/@comment-10541616-20140617230825

Actually the Pantheon would be there mainly just to harvest the planets inhabitants for new gene-sequences to fuel their war engine. Space Marines and xenos would probably intrest them considering how valuble their genetic codes are.

This sort of opperation is to known to the Pantheon as a "Red Harvest", in which they attack a single world in order to capture large amounts of it's population. And if they capture an ancient relic in the process, all the better.