what do we know about the LE-looking derse chess piece

You mean Jack English?  Well he was the B2 Jack Noir, he was cuaght trying to assassinate dream Jane and put in Prospitan jail where he stayed for 154 days.  Then he was sent a pumpkin with a bunch of knives and cutting utensils, Crowbar’s crowbar and Lil Cal in it.  Jack looked into Cal’s eyes and got possessed which caused him to stab out his own eyes replacing them with Cal’s and saw off his leg replacing it with a spire from his cell.  Then he killed Jane and Jake and was teleported to the furthest ring by Jade.  And that’s the last we seen him.