Corpse Rose is an Alchemical Ingredient. Combine 3 of these to grind them into Salts of Corpse Rose, which is used to make Thisobald's Brewed-Up Bellyglummer.

Missing its bottom jaw. And its body.
Properties
Rarity: Common
Weight: 0.2 kg / 0.4 lb
Price: 220 gp
Where to find
Total of 4 found in the Brewer's Alchemist stash. Exact location can be found in The Waning Moon from notes. Dug up from under a dirt mound in a patch underneath a house between House of Healing and road to Baldur's Gate entrance to the south