Synn is the main villainess of the Dungeons & Dragons games developed by Capcom. She does not appear in the first game Dungeons & Dragons: Tower Of Doom, but she is the final boss of the second game Dungeons & Dragons: Shadow Over Mystara.
Not much is known about Synn. She is actually a red dragon, who takes in the form of a beautiful sorceress in a red dress with a red cape during most of the game. She wishes to unleash a fiend upon the land of Mystara to cause destruction.
Although she does not appear by herself in Dungeons & Dragons: Tower Of Doom, her servant, the lich Deimos appears as the final boss of the game, in his attempt to achieve Synn's goals.
In Dungeons & Dragons: Shadow Over Mystara she is first mentioned in a cave in the stage 3-B, in the Vesuvia river, where it can be revealed (if the player chose the correct question) that in the first game, Deimos was in service of a red dragon named Synn. Then, she will appear only in the stage 6, where she will summon Deimos again to fight the player. After the lich's defeat, she will stun the player and won't appear again until the final battle in the end of stage 10. Then, she will return to her dragon form and try to eliminate the player until she is finally killed. After that, she says that even if she is defeated, she will be victorious due to the rise of the fiend, however, as the fiend fails to rise, her plans also fall with her.