Bastian (in-universe)
Bastian was a nudist writer who was erased from existence by the Shifting Chamber.
Biography
At a nude beach, Bastian was streaking, when he met Jenny Everywhere. They discussed nudism, and Jenny revealed that she was a shifter. She took him to a fantastical universe, then to her friend Laura Drake's house. Laura revealed that she had been making the Shifting Chamber, a machine that would allow non-shifters to shift just like Jenny, but she couldn't test it as it had to be operated from the outside. Bastian volunteered, but Laura had miscalculated and instead he was erased from existence. With no way to bring him back, Laura gradually forgot about him but Jenny vowed that she never would. (PROSE: A Day at the Beach)
Personality
Bastian found clothes "distracting", and so didn't wear them when writing. He was initially upset about being erased, claiming it was bad for his writing career, but quickly came to accept his fate. (PROSE: A Day at the Beach)
Behind the scenes
"Bastian" is an in-universe version of the real world writer of PROSE: A Day at the Beach. He decided to write himself into an April Fools story because he wanted to meet Jenny and felt that erasing himself from existence would make for an unexpected and darkly comic situation.