A Doomed player will unavoidably die when a certain time-based trigger occurs. The most common instance of this is the Doomed Townie, which will passively die Night 1. There is nothing that can be done to stop a Doomed player from dying at the designated time.
Because there is nothing to be done to stop a Doomed player from dying, many consider this a bastard role.
Doomed players have been seen as several different alignments.
What distinguishes Doomed from other roles and modifiers like Weak and Lovers is that Doomed players die at set times. This can either be a post count (after 24 posts have been made) or at a certain phase (Night 2). Conditionals may be set to determine whether the Doomed effect takes place; for instance, the moderator may allow a Doomed Godfather to live beyond its appointed time of death if it is the only Mafioso remaining.
Use and Power
For Town, it's pure negative utility and borderline pointless unless the Doomed player also has some kind of nice power role to balance it out. For scum, conditional Doomed modifiers can be used to balance a game such that the positive feedback from scum starting to come out ahead is limited.
In Bastard Mod games, Doomed players dying very early on (e.g. before the end of the first Day) may suggest that they are still participating in the game, though apparently dead.