Guildenstern is the self-proclaimed greatest Genma scientist. He is responsible for the creation of many of the Genma soldiers that the heroes fight throughout the Nobunaga trilogy.
In Onimusha: Warlords, he appears several times to talk with Samanosuke Akechi and tries to kill him using one of his demon creations like Reynaldo or Marcellus and Marcellus S. He doesn't fight himself, preferring to destroy his foe using his numerous creations. No one knows what happens to him after the defeat of Fortinbras.
Onimusha: Blade Warriors
Guildenstern returns in Onimusha: Blade Warriors. He creates and sends various creations to the human world, including Marcellus.
Onimusha 3: Demon Siege
He also returns in Onimusha 3: Demon Siege, with two missions. His first job is to work on the Timefold machine. This machine can control time itself. His master Nobunaga Oda ordered him to work on it so he can go into the future to rule over all the world and even time itself. Guildenstern also wants to create the ultimate and most powerful warrior of all the time to destroy Samanosuke. He then decides to use Ranmaru Mori to be this warrior. The scientist is then defeated by Samanosuke when they battle in the Zoo de Belogne stage.
- While he does not appear in Onimusha 2: Samurai's Destiny, he is referenced through notes. He is also responsible for the creation of the Golden Evil Statue that Jūbei Yagyū fought and destroyed in the game.
- Guildenstern is a character in the famous Shakespearean drama, Hamlet. Most Onimusha villains are named after the characters of the play of Hamlet.
Babian | Barabazuu | Barthah | Battobone | Battochyka | Bazuu | Brainstern | Dark Crow | Dark Puppet | Dark Spider | Demonic Skeleton Knight | Dongorr | Dorabazuu | Dordio | Dordo | Fobora | Fugaku | Fortinbras | Gajimaro | Gargant | Genma Tree | Gertrude | Gilzorm | Ginghamphatts | Gogandantess | Golden Evil Statue | Gorr | Guildenstern | Gyaran | Hecuba | Jujudormah | Marcellus | Mother Genma Tree | Nuraubis | Osric | Vega Donna | Zabiet | Zagat | Zmoh | Zolworm | Zombie Warrior | Zorm