The Investiture of the Gods definitely has many aspects that may be inspirational to Gloranthan referees, be it tales from the Godtime, heroquest ideas, magical weapons... There is a manga adaptation of it called Hōshin Engi, available in English (https://en.wikipedia.org/wiki/Hoshin_Engi). I have read both, and I recommend the latter if you're not ready to read a 1,000+ page long novel full of unfamiliar references.