en_tn/heb/12/24.md

the mediator of a new covenant

This means Jesus caused the new covenant between God and humans to exist. See how you translated this phrase in Hebrews 9:15.

the sprinkled blood that speaks better than Abel's blood

The blood of Jesus and the blood of Abel are spoken of as if they were people calling out. Alternate translation: "the sprinkled blood of Jesus that says better things than the blood of Abel" (See: rc://en/ta/man/translate/figs-personification and rc://en/ta/man/translate/figs-explicit)

blood

Here "blood" stands for Jesus' death, as Abel's blood stands for his death. (See: rc://en/ta/man/translate/figs-metonymy)