What is a person called who is playing an (online) game for another person as a paid service? [closed]
Solution 1:
This process is known as power leveling:
Powerleveling is a service offered by some geeks who take your money away and play MMORPG day and night, working in two or three shifts. In a month or two they can buff your character to the highest level available — Urban Dictionary
The term you want therefore is power leveler.