As Russian forces pillage occupied Kherson and Moscow rushes in reinforcements ahead of a looming battle for the strategic southern port, the city’s Kremlin-appointed proxy rulers dispatched a team to a majestic 18th-century stone cathedral on a special mission.

They were sent to steal the bones of Prince Grigory Alexandrovich Potemkin.

The memory of the 18th-century general is vivid for those in the Kremlin bent on restoring the Russian imperium. It was Potemkin who persuaded his lover, Catherine the Great, to annex Crimea in 1783. The founder of Kherson and Odesa, he sought the creation of a “New Russia,” a dominion that stretched across what is now southern Ukraine to the Black Sea, and when President Vladimir V. Putin invaded Ukraine in February with the goal of restoring part of a long-lost empire, he invoked Potemkin’s vision.

Now, with Mr. Putin’s army having failed in its march toward Odesa and threatened with being driven from Kherson, Mr. Putin’s grand plans are in jeopardy — but the belief among Kremlin loyalists in what they view as Russia’s rightful empire still runs deep.

So it was that a team of Kremlin loyalists descended into a crypt below a solitary white marble gravestone inside St. Catherine’s Cathedral.