Hi Meltedcharm, thanks for the submission. I quite liked the surrealism of the concept. I also like that it's deliberately short, as if we have caught the character in a moment of uneasy reflection.
My feedback is both thematic and technical.
Thematically, the spookiness is great, however it detracts from a sense of 'wonder' that readers come to the Wanderer's Library for. Perhaps elaborating on why the entity would want to steal shadows could solve this? There's no rule about this though, so I'm only speculating.
Technically there are some things that you could benefit from editing. Your sentences would flow better if they were structured more completely and less as fragments. Also, being a bit more consistent with pronouns will help the reader understand which character you are referring to, particularly in the opening passage. Was there meant to be a part where the protagonist regains their shadow again, or is it simply gone forever with no explanation? You may want to make that a bit clearer.
Overall a nice idea and congratulations on your first article submission. Best of luck!