Roland blows his olifant to summon help in the midst the Battle of Roncevaux holding Durendal. Painting by Wolf von Bibra (1862 – 1922) https://en.m.wikipedia.org/wiki/Durendal
See Also
https://en.wikipedia.org/wiki/Childe_Roland_to_the_Dark_Tower_Came
Etheric Force Identified as Dynaspheric Force