Dark Souls The Board Game: Asylum Demon Expansion - Rules of Play says:
As you pace the halls and corridors of the Undead Asylum it can be found to be a lonely and quiet place, moribund and uninviting. Here dwells a demon capable of lethal rage, its mind still ruled by virulent thoughts. Beware this foe. For all that you will fight stronger, more cunning, and more agile opponents, complacency will hasten your end at its hands all the same. Can you triumph over the Asylum Demon, or will your corpse soon be another to roam the Asylum with the hollowed?
The Asylum Demon Expansion is intended for use with Dark Souls™: The Board Game. This Dark Souls™: The Board Game expansion features a terrifying new mini boss and mega boss. Included are a new gigantic mega boss tile, deadly new boss behaviours, tokens for the new Pillar terrain piece, and unique new boss treasures. All the components provided are for use with the mini and mega boss encounters and offer two unique encounters!