Bunch of Keys (Resident Evil 4 Remake)

Four keys hung around a metal ring.

These keys are used by Ashley when you take control of her in Chapter 9.

Each key has one specific use:

The first key, the one with the snake-themed handle, is used to unlock the treasure chest located in the Mausoleum Armory Storage.
The second key, the one with the fish-themed handle, is used to unlock the treasure chest located in the Library.
The third key, the one with the botany-themed handle, is used to unlock the elevator on the north side of the Library in order to access the Small Library C.
The fourth key, the one with the crow-themed handle, is used to unlock the treasure chest located in Small Library C.