Magus is randomized in Jets of Time. There is a 1 in 7 chance that he'll stay unchanged, but in the other 6 of 7 times, he'll be replaced with a version of another party member. For the purpose of this page, we'll refer to the boss as Magus regardless of which character shows up. After Magus fades in, you are able to open the menu if you would like to adjust your equipment to defend against the correct element.

Magus's Magic Defense can be lowered by attacking him with Frog equipped with the Masamune (not the Grand Leon). Each time he is damaged, he will cast a spell to indicate a barrier change: the element of the spell he casts (it will be Lightning 2, Ice 2, Fire 2, or Dark Bomb) becomes his only vulnerability and he will absorb all other elements. He will remain vulnerable to physical attacks throughout, so if you aren't able to attack him with the correct element, a powerful physical Tech will also do well. Keep an eye on your party's HP, because all damage will counterattacked with a barrier change. On his turns Magus will also cast Geyser (damages the party and inflicts HP Down) or attack single party members with his weapon.

At 50% HP he will change phases. The earliest indicator of this is that after he takes damage he will stop counterattacking. At this point you can safely spam the element not blocked by his barrier and physical damage without fear of retaliation. Then on his turn he will cast Magic Wall (“Magus risks casting a spell”) to increase his Magic Defense. Now his barrier is completely gone and he may be attacked with any type of damage. However, on his next turn, he will unleash his ultimate move (see below). Using Magic Wall/Barriers or elemental Vests and Mail can help mitigate this attack, but if your damage output is high, it's likely you'll defeat Magus before he has a chance to use it. He will continue to cast Magic Wall followed by his ultimate spell until defeated.

Magus's ultimate ability (Dark Matter in vanilla) will be replaced with a different, attack, depending on which party member takes his place.

Note for playing with the Duplicate Characters (dc) flag: unlike your player characters, whose abilities are determined by the form they take as opposed to their palette, Magus's ultimate ability is determined by who the game thinks he is, ie the palette. If you see Crono with Frog's palette, the ultimate attack will be Hexagon Mist and not Luminaire.