Well, its not a big jump of logic to say he died.
-Lavos beat him down in Zeal, when Crono died.
-Magus was interupted by Crono when trying to summon him
-Nothing suggests that his spell would have still failed had Crono not interfered.
-Before Lavos showed up, Magus was not present in any timeline other than 600 in the war, and as Janus in 12,000bc.
-I never argued that
-I never argued that
-Nothing suggest that his spell would have work perfectly, if Crono and co. wouldn't have interfered
-Remember that nothing happens in Chrono Trigger before it actually happened, so since Magus hadn't already passed through any gate he wouldn't been in any other time era
Lol check this out:
Magus got to 65,000,000,000 BC hit his head and lost his memory, with time his hair returned to their original blonde color or something and was later called Kino