Durer is the warden of the prison, who is undoubtedly very twisted and demented person. He is the son of Bollanet, a high government official, therefore the abuse he inflicts on the prisoners is hidden from the public. While Durer certainly takes turns on most of the prisoners, he pays particular attention to Vallewida, but later on, Guys, too. He's an obvious brutal and heartless sadist, but some of his more complex emotions seem to come out when abusing Vallewida. He often gets frustrated with Vallewida for not remembering his past, for Durer knows Vallewida previously hid information that could prove how Bollanet, Guildias and himself were a part of the large wheat smuggling conspiracy. When abusing Guys, however, Durer shows less of a complex side and more of his meaningless sadistic side, especially in the scenario where Guys becomes his sex slave.
If Guys manages to clear his name and gather evidence proving Bollanet's involvement in the wheat smuggling operation, it can be assumed Durer, too, loses his position as warden and is thrown into prison himself.