Magic:Duration
A spell's Duration line tells the character how long the magical energy of the spell lasts.
Timed Durations: Many durations are measured in rounds, turns, minutes, hours, or some other increment. When the time is up, the magic goes away and the spell ends. If a spell's duration is variable the DM rolls it secretly.
Note: Avlis spell durations are all measured in "Real Life" seconds or minutes. "In Game" time (i.e. the 20 RL minutes per game hour server setting) has no effect on spell durations. There are no "Hour per level" or "per Day" spells in Avlis (any effects that still use the game hour as a measure of time are either special exceptions, or bugs). The term "turn" also has no meaning in NWN, and should always be replaced with "minute". A "round" does have special meaning in NWN, but as far as spell durations, it is simply "6 seconds".
Instantaneous: The spell energy comes and goes the instant the spell is cast, though the consequences of the spell might be long-lasting.
Permanent: The energy remains as long as the effect does. This means the spell is vulnerable to dispel magic.
Concentration: The spell lasts as long as the character concentrates on it. Concentrating to maintain a spell is a standard action that doesn't provoke attacks of opportunity.
Anything that could break the character's concentration when casting a spell can also break the character's concentration while the character is maintaining one, causing the spell to end (see Concentration, below). The character can't cast a spell while concentrating on another one. Sometimes a spell lasts for a short time after the character ceases concentrating. In these cases, the spell keeps going for the stated length of time after the character stops concentrating. Otherwise, the character must concentrate to maintain the spell, but the character can't maintain it for more than a stated duration in any event.
Subjects, Effects, and Areas: If the spell affects creatures directly, the result travels with the subjects for the spell's duration. If the spell creates an effect, the effect lasts for the duration. The effect might move or remain still. Such effects can be destroyed prior to when their durations end. If the spell affects an area, then the spell stays with that area for the spell's duration. Creatures become subject to the spell when they enter the area and become no longer subject to it when they leave.
Discharge: A few spells last for a set duration or until triggered or discharged.