Personally I forgot because we get his physical description only once or twice, but Goldie Gramps repeatedly. When I saw the art I was like oh yeeeah he does look that pretty doesn't he.
Him being a grandpa was too embedded in my brain.
Oohh i get that. It just engraved in our brains (≧▽≦) in my case, i think the phrase "whales looked ugly in comparison" stuck to me. When I read that I thought" this grandpa must be the most beautiful being in this world then!" (≧▽≦) (Also didn't help that in all media I consume, dragons were mostly described as looking young and beautiful even when they're thousands years old ಥ‿ಥ just like with vampires lol Ineedmoredilfandgilf)
Finally goldie grandpa!!! Exactly as how imagined him to be (｡♡‿♡｡)
Also how did others imagine eru as old like a grandpa or anything else other than an ethereal being. He was literally described as more beautiful than the whales in the novel. "The elf was so beautiful that even the whales looked ugly in comparison." (≧∀≦)