Other demons were seen in Demonopolis to enjoy normal jobs that wouldn't be out of place in the real world. Rough Schwartz and Egger were Demon World's immigrant control and would impose very harsh measures on visitors who didn't have the right paperwork. Drum is the landlord of The Shame Inn and is a very loyal supporter of Grimomen. When he believes Shion to work for Grimomen, Drum happily gives away all the information on how to find the winged demon.
Grimomen's plan was to use magic to turn human warriors into demon ones that will happily kill on his command. Furthermore, he wished for Shion to become a demon and be his right-hand "man". When Shion destroyed his wings, Grimomen decided to kill Shion instead, but Shion got there first and ended his rule of Demonopolis. With Grimomen gone, it is unknown who filled the void and who exactly Drum looked upto from then on.