Go to patheon enter top right portal to heliseum go right untill the blackmarket middle portal enter portal with statue right into castle and go the farthest right portal and keep going foward untill you cant from there enter the portal and choose the enemy
He drops the Heliseum equipment (then again so do Treglow and Victor *who are Velderoth's subordinates*) as well as a VERY low chance to drop the Nova equipment as well, personally I find Victor to be the easiest of the 3 to farm since he just STANDS THERE. I've gotten 8 drops in an hour from him on 2x drop with a giant spider familiar
What is the prequest?[/quote]
There's a LOOONG chain of quests leading up to the point where you can kill each of the mini-bosses.
You start by going to Parthenon through the big portal at the Six-Way Crossroads and finding the leader there.
Then you do about 100 more quests, and THEN you can kill Velderoth.
Apparently you can enter Magnus' room any time and try to kill him whenever.