Poorly drawn Deltarune darkner OC (name and lore under the cut)
He's called "The Stringpin" and he's the dark world form of Asgore's conspiracy board, manifesting as a mob boss who runs the Flower Kingdom's criminal underworld (which is totally a thing because I said so) from the shadows using a complex network of connections. This is represented by the red strings extending from his lower half, which form an intricate web reaching to every corner of the dark world, snaking through scenery and architecture to remain as inconspicuous as possible. If he were a real character in the game you'd be able to see his strings in the background all throughout the chapter (including the red strings already actually in the game found throughout Flower Castle) before eventually discovering they all lead back to him. There might also be some lore connection with the puppet strings from the Spamton NEO fight but I'm not sure how that would work exactly.
Since Kris was the one who made the fountain in Flower King and it's heavily implied that dark worlds are influenced by the minds of their creators, Stringpin is naturally reflective of how Kris seems to detest Asgore's obsession with uncovering the truth behind the incident - hence it manifesting as a dangerous, manipulative crime lord. Of course, as is often the case with darkner antagonists, Stringpin himself believes he knows what's best for the lightners his actions impact. He thinks Asgore is right that the only way to fix everything is by proving what actually happened on that terrible day, making him an opposing force to both the flowers, who want Asgore to focus on enjoying the dark world's fantasy, and Kris, who wants Asgore to just stop pushing everyone away. The dangling red strings with Asgore's notes on them in Flower Castle are Stringpin's way of trying to help him towards this end, dangling his work in front of him like a lure to draw his attention back towards his work and away from any distractions.
Given his motives, it's quite ironic that the Stringpin is himself a highly enigmatic and secretive character. Almost like it's some sort of metaphor for Asgore's own reclusive behavior or something...