en_tn_condensed/rev/06/12.md

the sixth seal

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

as black as sackcloth

Sometimes sackcloth was made of black hair. People would wear sackcloth when they were mourning. The image of sackcloth is meant to lead people to think of death and mourning. Alternate translation: "as black as mourning clothes" (See: rc://en/ta/man/translate/figs-simile)

like blood

The image of blood is meant to lead people to think of death. How it was like blood can be stated clearly. Alternate translation: "red like blood" (See: rc://en/ta/man/translate/figs-simile)