Certámen was designed to pit power against power with out causing physical harm to the combatants. Therefore, the duelists attack one another’s Quintessence Loci, not each other’s bodies. Even so, certain certámen duelists throw feints at their opponents, trying to unnerve the rival mage with an apparent attack upon his person.

In this case, count the attack as a Psychological Warfare maneuver (above), using the Social Trait + Gladius Sphere. In story terms, it looks as though the Gladius flares up and goes straight for the rival duelist. A successful roll puts that duelist on the defensive, forcing him to roll his Willpower or else lose his next attack. (If the roll succeeds by three successes or more, the Storyteller might subtract a -1 penalty from the defender’s Willpower roll for every success rolled by the attacker.)

Unless the duel has already been established as an all-out grudge match, actually attacking a rival mage in the certámen circle, with intent to injure him, is extremely poor form. The Marshall will probably stop the match right there, award victory to the defender, and charge the attacker with either a low crime (if the opponent isn’t harmed) or a high crime (if he’s badly harmed). In either case, the attacker will be banned from certámen matches for the foreseeable future, as she clearly cannot be trusted in them.