So I was playing Prodigy(Yes, the math game. Yes, I still play it. It's peak - sue me), and then they added this item into the game. LOOK AT THE DESIGN. THAT IS THE THORN RING. What it is doing here, I don't know. But it is here. Also, it describes it as a "Ring of darkness", so it's even MORE similar. Somebody on the Prodigy dev team definitely likes Deltarune. In addition, it literally lets you use a move called "Dark Sap", which heals you. IT SAPS AWAY STRENGTH. IT IS LITERALLY JUST THE THORN RING. Finally, there are LITTLE BRANCHES on it, like THORNS.
