Radahn is first encountered in Caelid, a once-verdant area that has been reduced to a red, highly-toxic wasteland by a fellow demigod, Malenia the Severed, in a last-ditch effort to defeat him.

Defeating Radahn, while optional, is required for the player to obtain one of the game's Great Runes, shards of the Elden Ring necessary to proceed the storyline.

Starscourge Radahn was the child of Radagon - a red-haired champion of the game's Golden Order faction, who worship a cosmic entity known as the Greater Will - and Rennala, queen of the Carians, a group of moon-worshiping nobles and astrologers predating the Elden Ring who draw power from the stars.

While Radagon resented his red hair as being similar to that of the Giants and their Fell God, who had once posed the greatest threat to the Golden Order, Radahn viewed it as a positive, believing it indicative of heroic qualities.

[1] Over the course of his life, Radahn is reputed as the mightiest demigod, an honorable warrior, an intelligent tactician, and a powerful sorcerer, gaining the respect and fear of many for his greatness.

While known to enjoy battle, Radahn is noted to be kind, admired by many for his noble qualities, and is a caring leader to his personal army, the Redmanes.

[2] Due to the constant threat of meteors bringing monsters to the Lands Between such as the Fallingstar Beasts, Radahn used his gravity magic to "challenge the stars", succeeding in a "crushing victory" and halting their movement entirely.

Upon the advent of the Shattering, a war following the attempted destruction of the Elden Ring, Radahn may have lost control of the capital of Leyndell to the demigod Morgott and retreated to Caelid.

This immediately causes the stars to snap back into position, allowing fate to resume for Ranni the Witch, and results in a large meteor impact that unlocks an underground city.

Saying that his current form is "a pale facsimile" of the brilliant general he formerly was, he called Radahn's reasoning for learning gravity magic - to continue riding his prized horse, Leonard - "adorable".

He also praised the fact that Radahn's defeat added a "permanent geological feature" to the game's map, allowing the player passage to the city of Nokron.

[16] Similarly, Robert Zak of DualShockers noted that the first Radahn battle broke the rules of Souls fights to that point, saying that it was the moment he most wished his non-Elden Ring-playing friends got to experience.

[19][20][11][21] Both praised and criticized for his highly aggressive and relentless moveset, Radahn has been considered the strongest boss in the DLC,[22][23][24] the whole game,[25][26][27] or even in FromSoftware's history.