The Commandant of the Sable Company Marines and the heir to House Endrin, Marcus was the next in line to succeed the missing Seneschal Neolandis Kalepopolis. He stood in for the seneschal during Queen Ileosa’s disastrous coronation ceremony and had been conducting a quiet search for Neolandis, though he began to lose hope that the man was alive.

During the investigation into the blood veil plague, Marcus and a squad of Sable Company marines managed to breach the Gray Maiden perimeter around the Hospice of the Blessed Maiden and reach the party. Upon being up to speed about Davaulus’ crimes and the treatment of the Gray Maidens, Marcus was furious—his sister joined the Maidens. He took the captive Dr. Davaulus, the indoctrinated Remmy, and one of his marines and flew out of the hospice to convince the Queen to have her soldiers stand down.

Marcus was later murdered by Queen Ileosa after attempting to assassinate her at a public ceremony.

Marcus was the eldest son of Marcellano and Vibia Endrin, who survived him only to perish during the Boggard attack. He is also survived by a brother, Telus, and a sister, Valeria.