Radiance is a Diablo 2 Resurrected runeword created by combining nef + sol + ith into a 3 socket helm. It requires at least level 27 to equip.
While being a better defensive option, Lore is generally a better option due to the skills bonus. If you are struggling with survivability or Mana, Radiance could be the better option.
Did you know? It takes on average 13 countess runs on Nightmare difficulty to get this runeword.