Thamar was the daughter of Nikephoros I Kommenos Doukas and his second wife, Anna Palaiologina Kantakouzene. Her father was the despotes of Epirus, which in current times is a part of Albania and Greece. Not much is known about her early life, and we don’t have a surviving portrait.
She was married to the fourth son of Charles II of Naples, Philip I of Taranto at L’Aquila in August of 1294. She had her first child Charles in 1296, suggesting she was at least in her teens when they married. They would have a total of six children. It was not a happy marriage. Five years into their marriage Philip was captured by Aragonese forces. Thamar had to beg her family in to pay for the ransom for his release and eventually pawned her coronet. He finally returned in 1302. Thamar was also forced to become a Catholic even though it had been settled at the time of her marriage that she could retain her own Orthodox faith. Her Catholic name was Catherine.
During a conflict between the Angevins (ruled by Thamar’s brother) and Epirus Philip became highly suspicious of his wife, even though she had pawned what was left of her jewellery to help pay for the military. Philip decided he had wanted to divorce Thamar and he accused her of committing adultery in 1309. She had just given birth to their last child in the same year. He forced her into confessing she had slept with forty Lords of the court and with one important Lord, in particular, the Grand Chamberlain. The marriage was quickly dissolved, and Thamar was shunned. She either turned to religious life and was imprisoned by her former husband. Either way, she would die shortly after in 1311. It is not known whether she died of natural causes.
Philip went on to marry Catherine II of Valois, who was also the titular Empress of Constantinople. They went on to have four more children.