From: House of Zeor
An ornament or design composed of three lobes, divided by cusps, radiating from a common center. Source: House of Zeor, Ch 4) "The trefoil is used to mark the graves of martyrs."
(Source: Index card file. "Donation" by Jean Lorrah, from AMBROV ZEOR fanzine #3) Grave marker which indicated who had died as martyrs to the cause of Unity (of Sime~Gen living together in a Householding.)