THEY have watched over the high moors of Glenlyon for thousands of years as part of a ritual that goes back to pagan Scotland.
And local legend has it that "strange and terrible" things will happen to anyone who disturbs the peace of the three ancient carved stones at Tigh nam Bodach.
But a development company has now been warned that it risks invoking the curse of the Cailleach - the old woman and protector of the glen - if it pushes ahead with plans to build a hydro-electric power station in one of the remotest parts of Highland Perthshire.
The English-based owners of the Auch estate in Glenlyon have applied to build the power station using water from four burns in Glen Cailliche - the Crooked Glen of the Stones - north of Loch Lyon.
The 40-acre development would involve constructing a weir on the Allt Cailliche burn, together with a turbine house and an overhead power line to connect with the national grid.
However, the project has met with nearly 60 objections, with protesters fearing its impact on the nearby Tigh Nam Bodach site. This comprises a miniature stone "house" which contains three bell-shaped stones, up to 18 inches high, representing the Cailleach, or old woman and divine goddess, the Bodach, or old man, and their daughter Nighean.
Continuing what is believed to be the oldest uninterrupted pre-Christian ritual in Britain, the water-worn figures from the River Lyon are taken out of their house by estate staff every May and faced down the glen, and returned every November.
The ritual marked the Celtic fire festivals of Beltane and Samhain and the annual migration of Highland cattle on and off the hills. In his Companion Guide to Gaelic Scotland, Professor Derrick Thomson wrote of the idols: "If propitiated (appeased] in the correct manner, they were believed to bless the stock and the pasturage and to ensure good weather - a prerogative of the Celtic mother goddesses."
The Glenlyon History Society is organising a protest walk to the stones next Sunday to coincide with Beltane as part of its campaign to stop the site becoming a "semi-industrial landscape".
Society secretary Jamie Grant said the Cailleach had protected the cattle grazing over the high ground, but "strange and terrible" things were said to happen to anyone who dared disturb her wintering grounds in Glen Cailliche.
Dr Anne Ross, an ethnologist who took away one of the stones for closer study without permission some 30 years ago, had a "very disquieting experience", Grant said.She returned it to the gamekeeper who looked after the stones "looking really distraught and dishevelled - as if she had been haunted".
Grant said the high-pitched whine from the power station "will fundamentally alter the 'soundscape' of the glen".
Scottish folklore expert Dr Margaret Bennett compared the plans to building a windfarm beside Stonehenge. She said: "This is regarded by many as a sacred site. The plans would destroy the setting of one of Scotland's most important sites."
The John Muir Trust (JMT) and the Mountaineering Council of Scotland (MCS) have also lodged objections over the damage they said the power plant would have on the remote area.
Documents submitted with the planning application, which is being considered by Perth and Kinross Council, admit that construction work "might affect" the stones site, and "the presence of the overhead lines would slightly affect the setting of Tight nam Bodach".
Miller Harris, agent for Oxfordshire-based developer Glen Meran Farming, said: "We would prefer not to comment at this stage."