Custodian, defender, or guardian
Warden
A warden is a custodian, defender, or guardian.
Warden is often used in the sense of a watchman or guardian, as in a prison warden. It can also refer to a chief or head official, as in the Warden of the Mint.
Text adapted from Wikipedia, CC BY-SA 4.0. Photograph: Dietmar Rabich (see Commons), Wikimedia Commons.