Intimacy
That scene is an extension from the episode in season 4Season 3 where QuintinQuentin and ElliotEliot live 50 years together to find the true meaning of life so the key will reveal itself (A Life in the Day).
Once they get the key, they teleport back to the throne room which is where ElliotEliot faced his greatest fear. QuintinQuentin reveals his love for ElliotEliot and suggests they actually have a real relationship together. ElliotEliot has had friends, but always kept them at arms length. He never had a real, serious, intimate relationship with anyone and the idea terrified him.