Honestly, even his voice work. Vigo the Carpathian was just some hammy one-off villain for the Ghostbusters, but there's still so much in Von Sidow's vocal performance. He captures that epic vibe of some D&D baddie that has chased immortality and paid a heavy price, but is still willing to double down on his pursuit.

I think he was a bit underutilized in his later years. Appearances in things like Star Wars and Game of Thrones could have been so much more impactful. As you said, a mortality and search for meaning, that's precisely what those two respective characters brought. They were just left under-cooked by the screenplay.