the fourth seal

"the next seal" or "seal number four" (See: rc://en/ta/man/translate/translate-ordinal)

the fourth living creature

"the next living creature" or "living creature number four" (See: rc://en/ta/man/translate/translate-ordinal)

"grey." This is the color of a dead body, so its color is a symbol of death.

Here "the earth" represents the people of the earth. AT: "one-fourth of the people on the earth" (See: rc://en/ta/man/translate/figs-metonymy and rc://en/ta/man/translate/translate-fraction)

A sword is a weapon, and here it represents war. (See: rc://en/ta/man/translate/figs-metonymy)

This means that Death and Hades would cause the wild animals to attack and kill people.