To rend something is to rip it into pieces. It changes to rent in the past tense and in the (uncommon) past participle. Rend has a figurative definition of tearing as well, which allows for a heart to rend in literature and for a sound to rend the air. The word can also be used without an object.
Rend is an old word with its first known use being before the twelfth century.
Examples
If we’re talking a physical match between the two, the Alien would tear the Predator to pieces. The Alien would rend [the Predator] limb from limb. [Yahoo Movies]
Chants of ‘Ganpati Bappa Morya’ rent the air as the city residents welcomed Lord Ganesh with pomp and fervour on the occasion of Ganesh Chaturthi on Friday. [Times of India]
It was at the very end that the onlookers exploded into thunderous applause and rent the air with a cheer that marked the highest point of the day’s enthusiasm. [Redsox]
When the ark of God was taken by the Philistines, and the two sons of Eli were slain, that there ran a man out of the army to Shiloh with his garments rent and dust upon his head (1 Sam. 4:11, 12), signified mourning over lost Divine truth and Divine good; for, as the ark represented the Lord’s kingdom, and in the supreme sense the Lord Himself, and hence the holy of the church, the rent garments signified mourning over lost Divine truth; and dust upon the head, over lost Divine good. [Bible Meanings]