When the fourth seal is opened, a terrifying horse appears. In the ancient world, a pale green color was used to show the color of a dead body.
Hades: In Greek thought, Hades was the underworld for spirits without bodies. The Hebrew concept of Sheol, the place of the dead (1 Samuel 28:15), was similar.
The death of one-fourth of the people on earth shows that the final judgment has not yet come (contrast Revelation 6:16–17).
This set of four woes (sword, famine, disease, and wild animals; compare Ezekiel 14:21) summarizes the hardships of life on earth. The world cannot provide hope for humanity.