Ksitigarbha

synonym: Earth Store Buddha
"Name of a Bodhisattva who saves suffering beings in the hell"

Ksitigarbha or 'Earth-Womb' is more popular in the Far East than he ever was in India. From a bare mention in the roll of the Eight Bodhisattvas, he has risen, in Asia, and especially East Asia, to a popularity second only to that of Avalokitesvara. The reasons for this development are obscure. As his name suggests, Ksitigarbha is connected with the depths. Like all Bodhisattvas, he aspires to deliver sentient beings wandering astray in the five(or six) paths of mundane existence; but he specializes in delivering them from hell. This expresses an extremely profound and esoteric aspect of the Bodhisattva's compassionate activity: he takes upon himself the fearful task not merely of plumbing the depths of existence, and bringing relief and consolation to those in torment, but of personally transforming and uplifting the vast inchoate mass of fear, hatred and despair swarming and pollulating in the pitch darkness of the Abyss. He is that loving 'compassion' of the highest to the lowest which, abandoning its own bright seat, does not shrink from working under conditions the most difficult and appalling--amidst scenes of horror, madness and desolation--at the seemingly hopeless task of reclaiming what is 'irrecoverably' lost. Ksitigarbha is the principle of spiritual sublimation in its most radical aspect, powerful enough to transform not merely hell into heaven but the foulest dregs of the Samsara, even, into the pure radiance of Nirvana. He is the supreme embodiment of spiritual optimism, the most profound development of Mahayana universalism, which wills that not so much as a grain of dust should be left outside the scheme of salvation.

Famous quote
"Not until the hells are emptied will I become a Buddha;
Not until all beings are saved will I certify to Bodhi."

(From "The Seeker's Glossary of Buddhism")