The Prose Edda on Hermod
The Younger Edda: > Chapter Xv. > The Death Of Balder.
attestation: Hermod the Nimble, Odin's swain, undertook the journey to Hel riding Odin's steed Sleipner
"he is called Hermod, the Nimble, Odin's swain, who undertook this journey. Odin's steed, Sleipner, was led forth. Hermod mounted him and galloped away."
attestation: Hermod rode nine nights through deep dark valleys on Sleipnir before reaching the Gjallar-river
"he rode nine nights through deep and dark valleys, and did not see light until he came to the Gjallar-river and rode on the Gjallar-bridge"
attestation: Hermod found Balder sitting in the seat of honor in Hel's hall
"Hermod rode on till he came to Hel's gate"