" You’re right, poltergeists are the third classification. They’re not an entity in their own right, though. They’re altered versions of either spectres or imprints. When a ghost becomes highly emotional—if a researcher taunts them, for instance, or if they see a scene strongly reminiscent of a powerful moment from their life—they can gather additional energy and start affecting the physical world. Usually, that manifests as objects being thrown or as gusts of wind. Sometimes, poltergeists will try to touch you, which I’m told feels like an ice cube being run over your skin. "

― Darcy Coates , The Carrow Haunt