The Incense Cage (Magic Cage)

Recently created by a little known invoker, the incense cage is designed to form an barrier through which spirits cannot pass, so as to keep them inside or outside of the area.
The cage is created by burning a certain mixture of herbs and minerals in four brass braziers, arranged in a square no more than fifteen feet along each side. The sickly purple smoke which issues from the braziers forms a barrier which spirits find extremely difficult to penetrate (none with less than 5 Hit Dice may pass through, and those with 5 Hit Dice or more attempt to cross once per turn, rolling to save vs. spell to determine whether or not they pass through). The area thus enclosed is generally a pyramid, 15' high in the middle, but wind and air movement can blow the smoke about and so can also change the shape of the area enclosed by these fumes.
The exact recipe for the special incense is thought to exist only in its inventor's spell book. If she were to sell any of the powder, she would demand at least 500 gp per pound (enough to maintain the cage for one turn): The price is not unreasonable, as this is the only method of dealing with spirits available to most nonshamans, and the ingredients are hard to find.
Over thirty different herbs and minerals must be mixed to form the incense, including spices from the east, powdered human bones, and a drop of dragon's blood, and they must be mixed with great care under special astrological conditions.
Rumors suggest that the inventor's apprentice or other servant has secretly copied the recipe, and is willing to sell it for the right price (at least 10,000 gp for the only copy). If these rumors are true, the Invoker is doubtless eager to recover her recipe and preserve her monopoly on its manufacture (so buyers should beware, but adventurers might find employment seeking it). Further, not just anyone could mix the ingredients correctly; Spellcraft and astrology proficiencies would both be required. 
Category:Shaman Magic Items
Category:Magic Items
Category:Magic Cages