Going off of Boarstorm's idea.
Level 1 Ranger, using a longbow, riding a hippogriff.
The ranger has 3 bags of holding, each holding 2000 arrows (10 arrows weigh a pound, bag of holding holds 200 pounds).
Round one:
Stay beyond 20 squares. Fire bow at Orcus. Fly 10 squares away.
Round two...