As explained under the heading Shaping the Spheres (Mage 20, p. 434), certámen duelists can shape their Gladius, Aegis, Locus, and glowing spheres into whatever forms they like. At the beginning of the match, this shape choice is essentially part of the ritual and isn’t counted as part of combat. Once the duel begins, however, it takes an extra effort of will in order to reshape the spheres into new configurations.

If a duelist wants to change sphere shapes in the middle of a match, that combatant should roll his Wits + Arete. The difficulty depends on whether he’s winning (difficulty 5) or losing (difficulty 7). A successful roll transforms the spheres as desired; a failed one keeps them in their current forms;

and a botched roll flusters the mage’s concentration, giving his opponent one free attack.