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A Storm of Swords (mentioned)|
A Dance with Dragons (appears)
The Winds of Winter (mentioned)
Marselen is the brother of Missandei. They had two other brothers. Both of them entered training as Unsullied, but one did not survive. He was purchased and then freed by Daenerys Targaryen. He is Naathi like his sister.
A Storm of Swords
Marselen is purchased with the rest of the Unsullied by Daenerys Targaryen and then freed. When Daenerys tells the Unsullied to abolish the practice of choosing a new name every day, Marselen goes back to his birth name.
A Dance with Dragons
His and Missandei's other brother, Mossador, is killed in Meereen by the Sons of the Harpy. Marselen remains Missandei's only living brother. When three free companies are formed of freemen, Marselen helps train the Mother's Men and is named their commander.