St Kessog was a royal from Ireland who worked as a itinerant bishop in the area around Loch Lomond. He established a monastery on Inchtavannach (’Monk’s Island’) an island in the loch which he used as a base for evangelism. He is said to have preached from a large mound in Callander in Stirling. He founded the church at Luss and was martyred there. An effigy of him can be found in the church.
He was the patron saint of Scotland before St Andrew.