A concentration-based spell’s Duration is as long as the mage applies mental effort to keep it going. The mage cannot take any other action, except for simple movement (up to his Speed; he cannot run). The mage also receives no Defense against attacks, although he can seek cover from ranged attacks. If the mage is attacked, a reflexive Resolve + Composure roll must be made for him to maintain concentration.
If the mage stops concentrating for any reason, voluntarily or not, the spell ends. The exception is if he decides to add Duration factors as if it were a transitory spell (see below) before the spell is cast, in which case the spell lasts for an additional time equal to its assigned Duration, and then lapses. The mage cannot start concentrating on a spell again once he has stopped, even if the spell hasn’t lapsed yet.
Note: A mage cannot use a concentration-based Duration when casting Aimed Spells[1].[2]
