 Mullaghmast was the royal residence of the Uí Muiredaig kings (later to become the O'Toole family), a sept of the Uí Dúnlainge dynasty of the Laigin.A rebellion had been launched by Rory O'More whose forces burnt Naas in 1577.The 40 lords of Laois and Offaly and their families were invited to a peace conference by Sir Henry Sidney on or around New Year's Day 1578; Sidney rose and left the unarmed lords and their wives, children and followers, and all except one were killed by Sidney's men, leaving the castle strewn with body parts and drenched in blood.