Unlike the trooping fairies, solitary fairies live alone and are inclined to be wicked and malicious creatures, except for beings such as the brownie who is said to help with household chores. A mixture of a mucus like excretion and leaf litter was used for the walls, the entire hive engaged in the task. Magpies they appeared attracted to colourful or shiny objects and presented them to their majesty.

Fairy trooping

classifications fairies

Many of these literary fairies seem preoccupied with the character of the humans they encounter. But the trooping fairies also include other fairies of lesser importance; a trooping fairy can be large or small, friendly or sinister. Merrylin found that the nest was plagued by some kind of fungal growth, hence the evacuation. The prospect of caste systems within faerie hives fascinated him and he wished to find examples in his own country.

Source: https://en.wikipedia.org/wiki/Elemental