The SetAILevel() NWScript command sets the "intensity" at which the AI of an creature should be operating. This does not work on player characters, nor on objects that are not creatures. Normally this command is not needed, as creatures will by default adjust their AI level in response to their circumstances (lower AI when no player characters are in the area, and higher AI when in combat). Its main use is for when the default adjustments are inadequate for some reason. If the AI level is changed from the default, it will remain at the specified level (the game no longer adjusts it due to circumstances) until it is explicitly returned to the default (using AI_LEVEL_DEFAULT).