Complex sentence: In times of clan warfare, a signal beacon was lit on the highest tower of Foulis castle to gather the clan under arms, hence the Munro slogan or gathering cry of "Casteal Foulais na theine," meaning Castle Foulis ablaze.
Split into simpler sentences: In times of clan warfare a signal beacon was lit on the highest tower of Foulis castle to gather the clan under arms. Hence the Munro slogan or gathering cry of "Casteal Foulais na theine," meaning Castle Foulis ablaze.