Marc Events

Starting Year 2, 1/1, he'll be with Hagel. (30 friendship)

15 days later, talk to Marc on Artisan's way, then visit Iksel's place. (Possibly optional.)

30 days later, go to Artisan Way. (40 friendship)

30 days later, go to Artisan's again. (45 friendship)

30 days later, go to Artisan's again. (50 friendship)

After Year 4, 1/1, with his level over 30, and 60 days later, go to Atelier Rorona. (60 friendship)

Go to Promised Land with Marc, fight Iron Giant. It isn't hard, especially not at endgame. Two days later, go to Atelier Rorona for the ''Arise, McVellion'' trophy. Marc is a jerk :D

If you don't want to trigger Marc's end, don't take him there.