I read it in 2000 and can't remember a title. It was about a a ship that was sent to another planet to figure out how to beat an enemy that was plaguing them. It would insert symbiotes in to select humans and it would give them control over elements. It was figured out that a human could only control 2 symbiotes max, like water and air and someone with earth and fire, or the symbiotes would gain control. Eventually someone accidently gets dozens into them and figures out how to control them and defeats this evil(can't remember specific entity), story over. That is the general story. When I read it, it was already in a big paperback with all three included. Any help would be great. I would love to purchase and reread it again.