Okay, here's a summary in conversational English:
You can change your own Look in Elden Ring Underfall, but not fully from the start; you gotta use something called Murk first.
More importantly, even if you started looking normal-ish, that might not last! See, it says something about changing appearances *after* the changes. The core point is: once things like "Sins" have been settled and your personal story unfolded during gameplay-- which definitely shapes your first Underfall Look -- then you