The first fight with Magus has one of the best setups in the game
The party thinks he is the responsible for Lavos existence and Frog must defeat him to avenge his fallen master, Cyrus.
You cut a mountain in half, break into his castle, defeat a samurai, a uhh... mage and an obese demon cheating ******* and finally reach his room.
And when the battle begins, and the musoc starts playing, you know you're up for some serious ****
Magus is no pushover, he has 6666 HP(yes, this was intentional), all elements of magic spells, a changing barrier and his most devastating attack, Dark Hole.
And after you beat him, a time gate opens and sucks the ENTIRE CASTLE into it, leaving Magus back in the Dark Ages and the party at the Prehistory.
Fastforward to after the Black Bird's events, Crono is dead, yadda yadda, you get it
You find Magus at the North Cape where he mocks Crono, angering the party and you're given two options, fight him, and if Frog is in the party, the battle becomes a 1v1No Items. Fox Only. North Cape.
Or not kill him, in which case he'll join your party and HOLY CRAP LOOK AT THOSE POWERFUL MAGIC SPELLS aaaand I'm out of TP