Straight from Castle Age
Demon Realm and Keira Boss
October 2, 2009 by Vulcan
If you are so lucky to get a drop from that quest, a new challenge awaits for you. On the Alchemy page, you'll be able to summon Keira for a truly challenging fight. This 10-man battle will be tough but the rewards will be epic. There might even be a way to sway Mephistopheles' minion to your side.
Before this point, the demon Realm had no subquests or a Special Mission. Instead, the 5 main quests there took forever to reach 100% influence (which you could only do once per quest). To get to 100% influence, It took about as long as it now takes to get to 100% influence for the main quest, and the two side quests 4 times. To say it a different way, without leveling up or using energy potions, it would have taken 30 days to reach 100% influence in each of the 5 quests.
People were somewhat... disappointed... with the change, and with all the energy they wasted on the Demon Realm.