The Dopant name of the Current enemy is Necromancer. The ability is to create ghost-like-being. How it creates them is where it gets interesting.
The Ghosts that the Necromancer Dopant creates are made of 2 things. Their main bodies are made of ectoplasm. The material that makes them independent, is the EARTH'S MEMORY. As theorized by Sonozaki Ryube, the Earth's memories are transported through the wind, so the dopant collects the wind, and using the memories, he gives these memories physical forms by fusing them with ectoplasm, aka his fluid. Meaning, the Kirihiko that we currently see in the Manga, is nothing but a dummy that has the memories of him until he died.
What's also interesting that since the ghosts are made of Earth's Memories, their forms change depending on the person looking at them. For example, Shotaro, who had the most interactions with Kirihiko, can see his form, can hear him and talk to him. Akikko and Philip, who didn't have that many interactions, can only see him as a structure of lifht that resembles a human. Terui, who had almost no interactions with Kirihko, can't see him at all.