Martin Setterholm was a xenobiologist born on Diadem, having traveled from the Sol system as a frozen, fertilized egg. Something of a loner, he became obsessed with the idea of emergent intelligence, of small simple elements combining to produce a sentient creature. He began to view the worms on Diadem as a part of a planet-wide consciousness, and believed that the harvesting of ice by the colonists was -- in a sense -- causing brain damaging.
Knowing he would be unable to convince his fellow colonists that they had to stop using ice as a fuel source for their fusion generators -- essentially, that they had to die -- to protect this alien life form, he went about introducing a toxic agent into their colony's life support systems. This caused them to lose mental awareness and focus, and eventually led to the deaths of everyone on Diadem save Setterholm.
Disguising himself as Iverson, a man he had killed personally with the sole purpose of assuming his identity, he froze himself in the distant hope that he would be found. Eventually he was, by the Conjoiner crew of the Sandra Voi. However, Nevil Clavain saw through Setterholm's deception, and killed him for murdering his entire colony.