One of the many ships used by the Collectors - servants of the Queen of Pain. According to legend, the Collectors are a group or sect who capture sadistic criminals and feed them to their transapient master, who punishes them with various forms of torment.
A common saying in some parts of the Middle Regions is 'If you see this in your sky, it means that someone is going to get eaten.'
And here is the Milton (the Collector Ship commanded by Kryslek and Skalosak) on its way to Avernus, home of the Queen of Pain.