Alp-luachra

Available sources (notably summaries of Robert Kirk's material) describe the Alp-luachra's behavior and typical circumstances of attack but do not provide a cosmogonic or mythic origin narrative for the being. The material situates it within Irish/Celtic accounts of fairylike beings that interact with human nourishment, emphasizing functional description (feeding on the nutritive essence of food) rather than an account of its creation, lineage, or place within a larger fairy polity.

Sources emphasise the Alp-luachra's usual invisibility and report a specific visible manifestation when it acts: it is said to take the form of a newt. In the descriptive accounts the creature 'sits invisibly' and when it feeds it 'appears in the form of a newt' and is said to crawl down a sleeping person's mouth. Thus the tradition conveys a being that is normally unseen but associated with a small amphibian shape during the act described in the sources.

Accounts (as summarised from Robert Kirk and later summaries) describe the Alp-luachra as consuming half of a victim's food not by eating the physical substance but by taking the 'pith or quintessence'—an unseen nutritive essence—thereby depriving the person of part of the effective nourishment. Its recorded mode of action is intimate and nocturnal/while-asleep: when a person falls asleep by a spring or stream the Alp-luachra appears in newt form and crawls down the sleeper's mouth to feed off the food they had eaten. The consequence presented in the sources is loss of part of the nourishment, reflected in the English descriptive labels 'Joint-eater' and 'Just-halver.'