Okay, here's how that works in Elden Ring Nightreign.
You can't just change whatever parts you want right away for your character. But when you have enough Murk resources acquired through gameplay and unlocking achievements within the side quest, you gain access to changing specific details linked to different "skins." Each skin corresponds with a chosen Nightfarer (playable character). You then customize which of those particular appearances that specific skin is wearing, using your collected M