When Magus joins the party, his HP takes a massive drop from his former boss forms, but his damage-dealing ability increases. He fights using a scythe as a weapon. His overall function is as a Black Mage type character (dealing damage with magic), but his physical stats are still higher then those of magically strong characters, such as Marle and Lucca. He is the only character in Chrono Trigger besides Robo that uses techs of different elements (and has at least one tech of each element), making him more versatile. His own unique Shadow damage techs are among the most powerful in the early game. Dark Bomb is the only level one spell that can hit multiple enemies and is stronger than any level two spell. His Dark Mist does the same strength as Dark Bomb but hits everyone on screen. However, his Dark Matter, while very powerful, is not as strong as the other final lvl3 offensive spells in the game like Luminaire and Flare. Black Hole can be useful against some of the nastiest regular enemies in the game, especially the Iron Maidens in the Dimensional Vortex in the DS version.
Magus, storylinewise, works well independently and his movesets reflect this. The only moveset he has that helps his party is Magic Barrier, which is best used on someone like Robo or Ayla. He is the only character that does not have a Dual tech (one of his main drawbacks). He is also the only character that cannot learn a Triple Tech naturally, mainly with Crono; his triple techs, Omega Flare and Eternal Darkness, require the use of special stones, such as Black Gemstone.
Because Magus' element is Shadow, he is vulnerable to Heaven/Lightning/Light damage, though as a boss he did not have this vulnerability.
Origin
Prince Janus was born sometime around 12,000 B.C. in the Kingdom of Zeal. Unlike his sister, Schala, he was more like his mother in that he was cold and distant. He is an introverted child, his only true friends being his sister and his pet cat, Alfador.
When Crono's party arrive in Zeal, they visit Enhasa, where they meet Janus. He tells them that the "black wind howls" and that one among them will perish, and then walks away from them. Later on, Janus and Schala converse. Janus mentions the "black winds", and Schala says that she feels "the foreboding" as well, though she tells him not to worry. She then gives him an amulet, saying that it contains her prayers. If something should happen to him, it would keep him safe. She says she wants to remain with him, but their mother has other plans for her.
Hearing this, Janus becomes angry and says she is not their mother anymore. Although she looks like her, she is not the same inside. Schala is then summoned by the Queen, so she leaves Janus and asks for his forgiveness.
Crono and party are imprisoned. Schala and Janus enter, and Janus comments on how they are idiots. Schala says that she wants to help them, though Janus thinks that they will not be of any use and does not want her to get in trouble if she lets them go. Schala says not to worry and that they may be able to help Melchior. Schala then frees them and tells them to flee the palace and save the Guru of Life, as he was sent to the Mountain of Woe for opposing Queen Zeal's plans.
However, the Prophet then enters the room, saying that he needs to put an end to them. Schala asks him not to do anything to them, so he concedes but tells Schala that she must cooperate with him. He then asks the party how they arrived in the Antiquity. They show the Prophet and Schala the Gate they came through. The Prophet throws them in the Gate and forces Schala to place a barrier on it.
After the Mountain of Woe falls into the ocean, Dalton arrives and takes Janus and Schala to the Ocean Palace. There, they see their mother's ultimate plan come to fruition.
When the Mammon Machine was activated, it began absorbing too much power. Queen Zeal and Schala along with the three Gurus were the only ones at the Mammon Machine's activation. The Gurus warned about of a dimensional vortex, a power humans cannot control, and they would be dragged into a rift in time, yet the Queen persisted in activating the machine. Soon, Janus entered the room for Schala. Suddenly, the six were transported in front of Lavos. Gates then appeared and transported Belthasar, Gaspar, Melchior, and Janus to different times. Belthasar was sent to the Future, Gaspar was sent to the End of Time, Melchior was sent to the Present, and Janus was sent to the Middle Ages. c. 580 AD.
In the Middle Ages
Janus was found in Truce Canyon by Ozzie, and three Blue Imps. He and his Mystics would have slain him had Janus not defended himself with magic, which human beings should not be able to use. Seeing the boy's potential as being a greater wizard than himself, Ozzie took him in and raised him, grooming him to become the Fiendlord and the leader of the Mystics' army. It was during this time that he took the name "Magus," referring to his status as a powerful magic user.
During this time, he grew vindictive and vengeful against Lavos and was eternally concerned over the fate of his sister Schala.
The War
His reasons for starting his war against Guardia are left out in the English version, in the Japanese version he said he was trying to gain power to have a better chance at defeating Lavos. Seeing his strong magics and strange appearance, most people took him to be a Mystic, himself.
At the height of the war, he faced Sir Cyrus and his squire, Glenn. Cyrus wielded the Masamune, the only weapon capable enough of breaking through Magus' magical barrier. Even with this, he was no match for Magus' powerful magic. He died in combat and the Masamune was broken. Glenn tried to avenge his friend, but was struck by one of Magus' spells and transformed into an anthropomorphic Frog.
He was attempting to summon Lavos during the war, and while the Mystics believed it was to help them win the war, Magus' real intentions were to summon Lavos so he could take his revenge on it.
The Battle in the Fiendlord's Keep
Eventually, after Frog gains the Masamune, the heroes (whom believed that Magus created Lavos because Lavos was said to have appeared in the Middle Ages) go to confront Magus in his castle. After fighting through his minions, he is fought and defeated. After hearing that he was believed to be trying to create Lavos, Magus informs the heroes that he was only trying to summon him. Lavos begins to wake up, and Magus tries to use his magic to send him back to sleep. Even he was not strong enough to kill Lavos when he awoke. The space-time distortion generated by Lavos' premature awakening created a massive and unstable Gate, which sucked everyone and the Keep in, scattering them through time.
Return to Zeal
While the heroes were sent to Prehistory, Magus was sent back to his own time. During this time, because of his knowledge of the future, Magus was able to convince his mother Queen Zeal that he was a powerful oracle, and called himself the Prophet. When he appears on screen at this point, he is wearing a dark blue cloak that mostly conceals his appearance, but if one looks close enough they can see Magus' boot and hair showing.
His aim during this period was to bide his time until the point where Lavos appeared and kill it. He sets himself up in Zeal as a councilor to the queen, waiting for Crono and the others to arrive from the future. He went through everything he saw as a child, going through the motions until the battle at the Ocean Palace would give him another opportunity to destroy Lavos.
When the heroes appear, Magus, out of spite for them, convinces Zeal that they are threats that have to be eliminated, leading to a battle with Dalton's Boss Golem. Whether the Golem wins or loses, the heroes are captured. Schala, however, is able to convince him to spare them, leading to them being sent through the time gate they entered in, after which Schala seals the gate shut. The heroes later return using the Epoch and enter the Ocean Palace where Zeal is trying to harness Lavos power with the Mammon Machine. Magus was also there, knowing that Lavos would appear. After Lavos breaks into the Ocean Palace, Magus throws off his disguise and tries to fight it, but is quickly overwhelmed. Somehow, he survives. After Crono is killed by Lavos, Schala opens a portal that allows everyone to escape.
He is not seen again until the Elder states to meet him in North Cape. Here, he reveals he is Janus (via flashbacks). He then mocks Crono's team for being defeated by Lavos. You can then decide whether to fight Magus, or not. If you decide to spare him, he joins the party, but in either case, he mentions that Gaspar could help you revive Crono.
In The End
Magus merely inserts his two cents for the remainder of the game with a few exceptions. In the scenario where Ozzie attempts to rule the Mystics on his own and continue the extermination of humans, Magus informs him that he was merely a tool used to his benefit. This angers Ozzie, and causes him to denounce his former boss. When Ozzie is finally defeated, he states that the past "is merely a dream".
