The Pandemonium Chalice is a special gear that can be obtained by collecting all Cipher Coins in the Plague of Shadows. Mona expresses uncertainty on whether she could create one even with all Cipher Coins. The Troupple King is elated to see the Pandemonium Chalice as he thought they had all been lost. He then gives Plague Knight the Pandemonium Cloak as a reward.
In the gear screen the Pandemonium Chalice replaces the Troupple Chalice. If Plague Knight never obtained the Troupple Chalice, the Pandemonium Chalice allows him to meet the Troupple King. The save file will also show that Plague Knight owns the Troupple Chalice even though it can still be bought from the Troupple Acolyte. Lastly even if the Player never obtained a Troupple Chalice Plague Knight holds one aloft when being covered with Ichor.