Two entries with the name Placidus.
Placidus
In the Norse Erex Saga, an evil Earl who tried to force Enide into marriage. Erec, whom the earl had thought was dead, awoke from unconsciousness while Placidus was trying to force himself on Enide. Erec rose up and slew him.
He appears in Chrétien’s Erec as Oringle.
Source
Erex Saga | 13th century
Placidus
In the German play, Merlin – Eine Mythe (1830), the Merlin story is set in the sixth century and portrays Merlin as a wise and prophetic druid who is able to see the future and has a deep connection to nature.
Placidus is a Christian hermit and spiritual advisor to Merlin’s mother, Candida. He appears in Act II, scene 2, where he and Candida discuss Merlin’s prophetic abilities and his plans to bring the Grail to King Arthur. Placidus is portrayed as a wise and understanding figure who supports Merlin’s mission and offers him guidance.
Source
Merlin – Eine Myth | Karl Leberecht Immermann, 1830