Question: When did Helena Kantakouzene, Empress Of Trebizond's husband die?
Answer: 1 November 1463

Recent research has led to doubts regarding her existence. David Megas Komnenos (– 1 November 1463) was the last Emperor of Trebizond from 1459 to 1461. He was the third son of Emperor Alexios IV of Trebizond and Theodora Kantakouzene