Here's how (overall) it sounds to me:
- Thousands of years ago Nidhogg, Nika and other Gods existed as physical beings in OPs world. They fought, death and darkness ensued. The land of Elbaph was not called Elbaph at this time.
- During the Void Century, war was common. War God Elbaph is the reason Giants and AGs were feared, because he started wars with his neighbors. The land he resides in becomes Warland Elbaph, named after him. He had Nidhogg's DF. He meets and fights Joyboy in this time period. They eventually become friends. Ratatoskr is NOT a DF at this time, and only becomes one after everyone dies in this era to guard Nidhogg's DF.
- Fast forward to now. Luffy and Loki are the successors of those fruits