As
arcane lock, except as described above. Additionally,
improved arcane lock closes all targeted doors or containers if they're open when the spell is cast, then locks them. Unlike most spells, the caster need not have an unblocked line of effect to each door targeted by the spell, but the caster must know the location of each door. Mages and
Techno Mages often use
improved arcane lock to simultaneously close and lock every door in a building, either to trap something inside or lock something out.