Made from leather, teeth and real human hair, it was worn by Alexander Peden, also known as Prophet Peden, one of the most charismatic preachers of The Covenanters who denounced Charles I as spiritual head of the church in Scotland.
The mask was found almost 200 years after his death in the Cumnock home of one of his descendants having been passed down through the generations of his family.
The disguise was to buy Peden time after Charles I declared war on The Covenanters with his successor to continue mass persecution of the movement during what became known as The Killing Time.
More than 350 ministers were forced from their churches and many became outlaws, preaching at open air services, or coventicles.
Continuing to spread their work was punishable by death but many refused to denounce their beliefs - and chose to die.
A masked Peden went on the run, preaching across the south of Scotland and sleeping in caves to evade capture.
All Scots were force to take an oath renouncing the Covenant, which also rejected the Episcopalian style of church government - which was run by bishops - should be dismantled and run by court councils and ministers selected by their congregations.
Peden spent almost 11 years on the run but he was ultimately captured at one of his services near Ballantrae and imprisoned for four years on Bass Rock in the Firth of Forth.
He was deported to plantation in Virginia but Peden jumped ship and escaped to Ireland. He returned to Scotland lived out his days in a cave near Sorn, East Ayrshire, the village of his birth.
His mask survived and was handed down through the generations of his family. It was discovered, along with a sword and a wig, at a cottage in Cumnock, East Ayrshire, during the 1840s.
The mask is on display a the National Museum of Scotland in Edinburgh.