The clouds began to open up now and he could see the horses of the Thunder people (the Wakinyan Oyate) coming toward him. He could not see the Wakinyan because they were hidden in the clouds, but they drove horses before them, each of which was connected to the clouds by leashes made from lightning. In front of the horses were the akicita, also called the Wakinyan wayaka ‘Thunder slaves’. The horses and the men were slaves of Wakinyan because they had been struck by lightning. They came to test his bravery, and he was instructed to hold the pipe toward them and it would protect him. He was afraid, but he did as the sacred person had instructed him and the clouds parted, going past on either side of him.

Oglala Religion, p. 138-139