For once, I will answer that one. Spirits and Elemental beings does not jointly guard a treasure. Elemental beings can never prevail over the site guarded by a spirit BECAUSE spirits exist on a higher plane or dimension than the elemental beings. So if a site is said being guarded by both elemental being and a spirit as claimed by a medium, most likely, you are being misled again. Also, spirit can never come and take over a site being guarded by an elemental being. In simple explanation, it is the dimension x,y,z. and the meeting point is our very own dimension.
Point to ponder: Does a spirit die? or do elemental beings die too? If you think about that, between the two in their present state, who is the immortal one?
Check the articles of Prof. Jaime Licaucho on the existence of the spirit and the elemental beings.
Better yet, check the medium. Does he really knew or understood what he had seen? Or he is just hardheaded, stubborn bluffer?
Learn from other's experiences.