blood
Blood is the fluid which contains life.
Leviticus 17:11 NKJV
For the life of the flesh is in the blood, and I have given it to you upon the altar to make atonement for your souls; for it is the blood that makes atonement for the soul.’
Spiritually, it has a mysterious quality in that it both ritually defiles and makes clean.
Hebrews 9:22 ESV
Indeed, under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sins.
Innocent blood in particular defiles a the land in which it was shed.