Invisible Stalker

This spell summons an invisible stalker from the Elemental Plane of Air. This 8-Hit Dice monster obeys and serves the spellcaster in performing whatever tasks are set before it. It is a faultless tracker within one day of the quarry’s passing. The invisible stalker follows instructions even if they send it hundreds or thousands of miles away and, once given an order, follows through unceasingly until the task is accomplished. However, the creature is bound to serve; it does not do so from loyalty or desire. Therefore, it resents prolonged missions or complex tasks, and it attempts to pervert instructions accordingly. Invisible stalkers understand common speech but speak no language save their own. The material components of this spell are burning incense and a piece of horn carved into a crescent shape.