The Blue Sigil was a mercenary company comprised of ogres that was based in Mog's Keep, near Longsaddle and operated throughout the North. Around 1358 DR, they were led by an ogre named Mog the Fist, whose keep bore his name.
The Blue Sigil was founded by Thorog, after his tribe had been repeatedly raided by adventures, brandishing unique symbols while being paid to kill ogres. He reasoned that if others could be paid to kill ogres, his tribe could turn the table and return in kind. Finding work was difficult at first, but the company garnered a reputation of reliability.
Thorog and his successors (of which Mog was the eighth) accepted lone ogres into their group, provided they passed an initiation. This had led to a fairly large population within the group.