The Nemesis is a unique feature in Champions Online and a rare example of a player-based villain, the process of which is amongst the more complex in any MMO - a Nemesis becomes a regular enemy of the player-hero after being created (at level 25) and will take an obsessive desire to get revenge on the hero after a confrontation.
The Nemesis can take any form the player wishes, using the same customizing features as they do to create a hero - however, the Nemesis is limited to three distinct personality types that determine how they will threaten the world.
The Nemesis can be a rampaging savage, a diabolical mastermind or a maniac - all of which have a choice of henchmen (known as minions) that will periodically ambush the player from time to time and leave clues that allow special confrontations with the Nemesis.
After a while, a player-hero will defeat their Nemesis, at which point it is possible to create a second - giving the player their own personal "Rogues Gallery" and the option to "reactivate" their original nemesis later.
At maximum level (currently 40) players can team with one another and face their Nemesis in large raids - having multiple Nemesis working together provides a unique challenge to higher-tiered heroes and provides a colorful array of brutes, masterminds, and maniacs to terrorize even the most battle-worthy of heroes.