Mewlips, Gorcrows and Huorns (Adventures of Tom Bombadil and LotR) are all groups of characters that don't get a lot of exploration in canon and don't, as far as I know, have any named individuals. Part of the scariness comes from their group identity - being surrounded by a forest of sentient trees, in the case of Huorns. Not sure "Solo" best describes this, but I don't think they work as a relationship tag because there aren't any individual characters...not sure how would be best to reflect this?