Sephira

Life is the twin sister of Death and the primordial embodiment of all Life in Creation. Having existed since before the Beginning, Life and Death often fight over who is older.

Life was summoned by DxD during Armageddon in order to help locate the Horseman, Death. Taking pity upon the life forms on Earth, Life decides to help DxD and provides them with a spell to track Death. After the Apocalypse, Life appeared with Death and began to take more interest in the events of Creation. Life reappears when the seal on the Leviathans begin to weaken and escape. She provides Issei and Irina with a spell to send them back to Purgatory.

A few years after the Apocalypse and the Leviathans, Life, along with Death, appeared in order to buy DxD time to get far enough to escape Tathamet's wrath. This results in her form and essence being shattered and sent hurtling across all of Creation.

Trivia

 * Life's appearance is based off of Mavis Vermillion from Fairy Tail.
 * Like her brothers, Life has an obsession with certain foods with hers being organic only food.