There are in-game shrines devoted to Ebonarm, and he's mentioned in other books. I've heard a rumor about the unjoinable faction called "The Citadel of Ebonarm".
Mara (AKA Marilyn Wasserman) had this to say about the book: "I believe Reymon Ebonarm was pictured as a Nord. He was worshipped as a minor deity, or hero saint if you prefer, in the Iliac Bay area. There's at least one shrine to him in TES: Daggerfall. Daggerfall was the last city that the Nords ruled during the First Era."
"Ebonarm is another of the Daggerfall beta testers' alter egos, in this case that of Raymond Whit Crowley, who wrote 'Ebon Arm'. His online handle was Barak Halfhand at that time, but that name came from a book so could not be used in TES."
The ground shakes. The great armies continue to wage their unrelenting battle. The battlefield is red, the rivers flow crimson, the sky reflects a deep pink. In the distance lightning flashes, and thunder sounds. Two huge ravens begin circling the field; their blackness is vibrant against the various shades of red in this vista of death and suffering. The bright flashes of light and rumbling begin to increase. The redness surrounding the battlefield begins giving way to a golden glow from the east, almost like a summer's setting sun. From the false sunset a massive golden stallion and single rider approach. All become suddenly still on the field of battle as both sides recognize Reymon Ebonarm, God of War, and the companion and protector of all warriors, also known as the Black Knight and his mighty steed War Master.
He rides into the middle of the blood soaked field and dismounts. He is a very imposing figure. His very tall and heavily muscled body is encased in ebony armor. His ebony helmet does not hide the flowing reddish blonde hair and beard which appear almost as shimmering gold, nor does it shield the steel blue eyes that seem to pierce all they fall upon. In his left hand he carries a massive ebony tower shield on which is emblazoned a fiery red rose. As he raises his right arm, all see an arm and a magnificent ebony blade which are extensions of each other. The fused arm and sword are a result and symbol of the wounds suffered by this god during titanic battles in the youth of this world.
The ravens come to rest on his shoulders. And, as the point of the ebony blade seemingly touches the sky, lightning flashes, thunder roars. Then total quiet descends and a shudder rolls through both armies.
The leaders of both armies approach Reymon Ebonarm and kneel. In turn they tell their reasons for this war. Each asks for the favor of the Black Knight for their cause. Reymon Ebonarm listens, but there is no acknowledgment that he has chosen to favor one side or the other in this fight. However, each of the leaders has heard the other state his position. And, each now knows that this war is baseless. They embrace and turn to their armies. They instruct their forces to bury their dead, tend their wounded and return to their homes.
Reymon Ebonarm mounts his great golden stallion, War Master, and again raises the ebony blade skyward and extends the huge rose emblazoned ebony shield to both armies. A massive chorus of cheers rises from the armies. The ravens again take to the air. Lightning and thunder follow him as he rides into the sunset followed by the two birds.
The armies do as they have been bidden. They care for their wounded and bury their dead. As they retreat towards their homes each warrior is sure that the great God Reymon Ebonarm, the Black Knight, has responded to their individual prayers for intervention. Each side has won, neither has lost.
As the armies depart the field, the rivers begin to run clear, and a single red rose begins to bloom near the grave of a fallen hero.