"like a grave yawning at judgment day in some old apocalyptic painting."
The Last Judgment, Michelangelo Buonarotti (1475-1564)
Public DomainThe Last Judgment, Michelangelo Buonarotti (1475-1564)

There is a great and long tradition of depicting The Last Judgment in religious art; probably the most famous example is Michelangelo's vast, overwhelming fresco in the Sistine Chapel, Rome, with the dark hellish penalties enacted upon the sinners filling the lowest portion of the painting.

The yawning grave refers to the raising of the dead for the final decision on their fate: