From ONUV, only wins if his target dies
The recipient of the Mark of the Assassin will normally announce this fairly early, thus painting anyone who directs unsubstantiated accusations at them as the Assassin. Other players, particularly vampires, would do well to claim they received the Mark of the Assassin in order to deflect any accusations as being driven by the Assassin’s agenda. However, if enough players do this, it erodes the real target’s veil of protection and allows the Assassin to direct suspicion against them.
With both the Assassin and his target both outed with high certainty in most games, the Assassin should serve as a rallying point of sorts. “Yes I’m an Assassin and I’m going to vote for my target who is a [villager or vampire], so if you want a [villager or vampire] to die then vote with me.”
If a Team Village player received the Mark of the Assassin then this focusing of votes on a single target is particularly important for Team Vampire. Vampires and Werewolves find it difficult to coordinate their votes since communication between themselves would result in their being outed as monsters ripe for lynching. The Assassin is uniquely positioned to help Vampires/Werewolves solve this problem since he can actively campaign against a Team Village player without attracting Team Village votes the way a Vampire/Werewolf would. Vampires/Werewolves can keep their own status confidential and simply follow the Assassin’s lead during the vote.
Note that the Assassin can give himself the Mark of the Assassin. This is often the best approach for the Assassin, since the Assassin can keep his role and mark secret, and then the Vampires, the Assassin and the Apprentice Assassin are all aligned toward the objective of killing the Assassin, often through an open majority.
What do you think? Leave your thoughts in the comments section.