Lovers are players who are linked to each other. If one Lover dies, the Lover(s) linked to it dies simultaneously.
Lovers have been known to be of any alignment. It is not at all implausible to have Lovers in Town-scum pairs.
Lovers are frequently used for balance purposes in Open Setups, and are featured in Polygamist.
Lovers can have a number of unannounced additions to the above definition, such as the ability to talk to each other or confirmation of each others' alignment.
Tragic Lovers are a rather annoying variant. One can be town aligned. The other can be scum aligned. Each lover can have two win conditions. It can win with its own alignment as its lover loses. Or they can win together, acting as their own faction eliminating all other scum and town players. One must be careful how they eliminate the other players. Eliminating all the town first means the mafia will win with the town lover loosing. Eliminating all the scum first is suggested, but should the town lover just want the win immediately, they can rat the scum lover out. Proper play is for neither lover to screw the other over. They should pursue winning together. To encourage proper play, moderators often tell the pair they must win together and remove their abilities to win separately. When the tragic lovers win together, all other players lose.
"O Romeo, Romeo! Wherefore art thou Romeo?"
"Sorry I was busy killing the rest of your family. What's up?"
Use and Power
Lovers are primarily used to either force players to work together or to hasten a powerful role's death. For instance, a scumgroup in a small game may be comprised of Lovers in order to prevent them from bussing each other, or a Cop may be a Lover to another player in order to increase the chance of them dying early enough that they cannot break the game.
A rough guess is that a Lover is worth two-thirds as much as an ordinary player.