'Game of Thrones' star Ian Gelder passes away at 74

Ian Gelder, best known for portraying the role of Kevan Lannister in hit series Game of Thrones, has died at 74 years old.

His partner, Ben Daniels, announced his death in an Instagram post early Wednesday, May 8 (Philippine time). "It is with huge huge sadness and a heavy heart broken into a million pieces that I’m leaving this post to announce the passing of my darling husband and life partner Ian Gelder," he wrote.

He revealed that Gelder passed away after a battle with bile duct cancer, which is also known as cholangiocarcinoma. According to the National Cancer Institute, it's a "rare disease in which malignant (cancer) cells form in the bile ducts."

Daniels referred to Gelder, who was his partner for 30 years, as his "absolute rock."

"If we weren’t together, we spoke to each other everyday. He was the kindest, most generous spirited and loving human being. He was a wonderful wonderful actor and everyone who worked with him was touched by his heart and light. I honestly don’t know what I’ll do without him by my side," he said.

Daniels recalled how Gelder dealt with cancer "with such bravery, with no self pity. Ever."

"He was remarkable and will be so missed," he added. "Rest well, my sweet Chianni."

Gelder appeared in 12 episodes of Game of Thrones. Aside from the drama series, he also took on roles in Doctor Who, Fifteen-Love, and His Dark Materials.

According to PEOPLE Magazine, his next appearance will be in the next installment of Interview With the Vampire this month as well as in the second season of The Lord of the Rings: The Rings of Power this year.