After winning the war, the Pandavas went on a pilgrimage to Mount
Kailash. They wanted Shiva to cleanse them of the sin of killing so many
people. When Shiva saw them he hid. When they couldn't find him,
Yudhisthira said, "I know you have hidden because we have sinned, but we
will not leave without seeing you." As they moved ahead, a bull
attacked them. Bhima started fighting it.
The bull hid his head within a crack in a rock. Bhima tried to pull him
out by his tail, but the body of the bull got separated from his head.
The body turned into a Shivalinga from which Shiva appeared and forgave
them their sins.
The linga is still present in the Himalayas and is called Kedarnath.