Hidden Catacomb Passageway (Roman Numeral 'X' Wall)

A concealed catacomb passageway behind a wall etched with a Roman numeral 'X'—a clue tied to the Ark symbol. The narrow tunnel is knee-deep in petroleum-slicked water, swarming with thousands of rats. The passage leads directly to a flooded burial chamber containing a knight's coffin engraved with the Grail marker shield. Kazim ignites the oil, unleashing a roaring fireball and rat stampede, forcing Indy and Elsa to submerge under an overturned coffin for air amid choking smoke and dwindling oxygen.