Sorry to hear he passed , he was a Great TV and film actor.
Some memorable roles are in;
The orig Star Trek Series (The Gamesters of Triskelion as Galt ) ,
A Trickster Genie in the orig "Twlight Zone" who's granted wishes that always have a bad side; aka he grants a poor shopkeepers wish to be the leader in a contemporary country so he turns him into Adolph Hitler in the last hours of the war.
Even his voice as "The Horla" in "Diary of a Madman" and Kanamit in "To Serve Man" was chilling.