Musca-resper poison is a scrapped item which was originally intended to be used during the fight with Duke Sucellus. This poison would have been made by mixing musca powder, resper powder, and salax salt in the fermentation vats within the asylum.
Presumably, different types of mushroom powders would have been needed to be mixed each time the player wakes Duke Sucellus up during subsequent fights, but was scrapped in favour of only using one type of poison, the arder-musca poison.
