Zig Zagged: Matthias is as vulnerable or invincible as the plot demands — in one episode he can be injured only by special magic weapons and in the next he trips over a pebble and breaks his foot so his comrades must take on the next dungeon without him.
Matthias uses buff spells to become stronger.
Matthias regularly exercises at least an hour a day, so he's actually pretty fit for a wizard.
Enforced: "This wizard character is too strong. We need to weaken him a bit."
Lampshaded: "I'm guessing Matthias skipped gym class. A lot."
Invoked: Matthias is told to stay in the back of the party's attack formation, keeping him out of the line of fire while giving him some range for his spells.
Exploited: Emperor Evulz recognizes Matthias' power. He orders his minions to focus their attacks on Matthias. Matthias is wiped out quickly as a result.
Discussed: "It seems weird that this guy can fire lightning, but a backhand takes him down just like that."
Deconstructed: Emperor Evulz recognizes Matthias' power. He orders his minions to focus their attacks on Matthias. Matthias wipes out much of the minions with his powerful magic, but he is eventually overpowered by the sheer numbers. His friends try to help, but they are disorganized and vulnerable by this surprise attack.
Reconstructed: Matthais' physical vulnerability reveals that magic is just another tool or skill, and that mages are just as human as everyone else.