Lars went through a lot of possessions. By ghosts and demons, but the most dangerous one by far was Febris (he calls himself KeAl and usually introduces with this name, because knowing the real name of the demon is giving some power over him, to the person who knows it.). Febris is a so-called “floral” demon, it has less to do with the fact that they appear to love plant and flower themed things, and more with the fact that they “grow” inside their host and then “bloom”. Killing the hosts in the process. They drain human’s health and power, causing a fever, apathy, delusions, pain in the organs where they decided to “plant” themselves. Depending on a person they can die within a week or two days, if they’re weak or small. Lars managed to get through the possession with Marcus’s help, but Febris had time to “plant” his son in Lars’s soul...