There is one set of black robes. A long under robe (such as you might wear around the lab: the sleeves are plain and wouldn’t get in the way of working at a table or mixing ingredients) and a plain black outer robe in slightly thicker material which has long elaborate sleeves such as might well get in the way. Poking around further you find a pair of sandals and some long, rather dirty stockings. Gah-CHA! but that’s dusty. There’s a loin cloth.
All are just crumpled on top of each other: the stockings still inside the sandals. Yes, very much as if someone just disappeared.
There is no second set of clothing.
Inside the alcove with the corpses… They are of varying ages and stages of decomposition but none have been preserved by anything special, just dryness. They probably lay in dry, stone tombs rather than being buried. Some are wrapped in shrouds. Some just lie in the clothes they died in. A couple have had their chests opened and organs removed: it’s not possible to tell what. One has had both legs removed. One has had both hands removed.