Is the Norse Prayer from 13th Warrior real or Hollywood?

Yes, it is real, to a degree. Michael Crichton made his own variation for the movie 13th Warrior, but the actual prayer is a Norse prayer dating back to the first century.

Lo, There do I see my Father

Lo, There do I see my Mother and

My Brothers and my Sisters

Lo, There do I see the line of my people back to the beginning

Lo, They do call to me

They bid me take my place among them in the halls of Valhalla

Where thine enemies have been vanquished

Where the brave shall live Forever

Nor shall we mourn but rejoice for those that have died the glorious death.