Magus, known in Japan as Maou (Demon King), is one of the main characters in Chrono Trigger, the role-playing console game developed by Square Co. He is the dark wizard waging war against the Kingdom of Guardia in 600 A.D. Magus was originally Janus (Jyaki in the Japanese version), the young prince of Zeal in 12,000 B.C. After an encounter with Lavos as a boy, he was sent through a time gate to the Middles Ages. Vindictive and vengeful against Lavos and eternally concerned over the fate of his sister Schala, he is portrayed as brooding, potent, and gloomy. He fights using a scythe, as well as a combination of all magic types. He is an optional character but nonetheless an iconic cast member of Chrono Trigger, has many fans, and appeared in three GameFAQs character battles.

The word "Magus" is the singular form of the word "magi," a Latin word serving as the root of the English equivalents "mage," "magic," and "magician." Magus's Japanese name Maou translates roughly to "demon king" and is more clearly identified as a title rather than a name.

Magus appears in Radical Dreamers as Gil, a shadowy and handsome member of the Radical Dreamers thieving group. He is depicted as masked and mysterious, though gentle and cultured. He has the ability to slip in and out of the shadows of the night at will. Magus as Gil was also slated to appear in Chrono Cross. However, as development of the game progressed, designers decided it would be too difficult to integrate his complex story into the plot. His character, renamed Guile (Alf in the Japanese version, possibly in reference to Magus' former pet cat Alfador), was thus altered to remove his Magus identity and was left in with no back-story, existing merely as a competent magician seeking enigma in the islands of El Nido. Missing Piece includes a number of discarded character designs for Guile, including one which is more-or-less analogous to Magus's appearance in Chrono Trigger (cloak, pointed ears, etc.), as well as one in which he appears as a teenage boy. As it stands, Magus is only mentioned in a letter to Kid from Lucca, in which she assures Kid not to worry as "Janus" is probably watching over her. Gil appears in Chrono Cross only in an easter egg designating the events of Radical Dreamers as having taken place in an alternate dimension. In the English version of this easter egg, Gil is referred to as "Magil."