The three who arrived first were the youngest of the Lords. This didn't imply that they were young, but that they were forced by people much older than them to go and test the waters.
They were all old men. Their beards were white and the hair on the top of their heads was nonexistent.
Without mana or Existence, the mechanisms used by practitioners to alter their appearances were rendered useless.
The appearance they maintained would be the same one they had when their bodies became immortal and their lifespans increased.
Damien was over a hundred. In Earth terms, he'd be an old man, but with a lifespan of infinity, he was extremely young. He also never attempted to alter his appearance. His current look was as natural as it got, so he wasn't affected.