In old Transylvania they were referred to as "Ghosslings" which basically means a swarm or school of ghosts. In old European books i think they were referred to "Tillings".
A tort of ghosts.
Ghost isn't a every day animal. This means that they don't actually have a name for a group of ghost. So the best term to use is in the question, 'a group of ghosts', or just 'ghosts' on it's own will be fine.
It is a group of people that capture ghosts that are scaring people.
The names of the green and gray pac-man ghosts Blinky, Pinky, Inky and Clyde are the primary group of fictional ghosts
13 Ghosts
The so called "ghosts" in the Ghost Dance are the spirits of our ancestors.
A person that doesn't believe in ghosts are called skeptics.
Collective nouns for ghosts can vary, with some of the more creative options including "a haunting of ghosts," "a wail of ghosts," or "a specter of ghosts." These terms evoke the eerie and supernatural qualities associated with ghosts. While there isn't a universally accepted term, these phrases capture the essence of a group of these spectral beings.
They are called poltergeists.
Phasmaphobia.
People who don't believe in ghosts are called skeptics. Skeptics typically demand scientific proof of something before they believe in it. As there is no scientific proof in ghosts, skeptics deem them as being unreal.
It is called 1408.