This watercolour illustrates a passage from chapter four of the Revelation of St John the Divine. The prophet describes a vision of a heavenly throne:

before the throne there was a sea of glass like unto crystal... round about... were four beasts full of eyes... The four and twenty elders fall down before him... and worship him that liveth for ever and ever.

The Book of Revelation is one of the most dramatic books of the Bible, and Blake was sensitive to its powerful imagery.