Nidhogg and Nika Possible Friendship
Jarul said that the warrior god fought against Nika, but that doesn't necessary mean they were enemies.
When Loki is in his dragon form, Ratatoskr is right next to Luffy, who's resembling Nika in his Gear 5 form, and seems happy alongside him.
If they were enemies, I would imagine that there would have been some animosity from his part, but nothing.
Plus Ratatoskr pats Luffy when he's scolded by Nami.
Personally, I can see Nidhogg and Nika having had a friendly rivalry akin to Roger and Whitebeard, fighting but with no harsh feeling on either side.
So when Ratatoskr saw Luffy in Gear 5, it was like seeing an old friend, one who he hasn't seen in over 800 years, possibly more if Ragnir wasn't used by anyone during the Void Century.
Plus, Imu called both of their names, and the two possibilities in my head right now is that either they were both his enemies or Nidhogg was an ally who had a heal turn near the end.
Not too mention that Jarul said that when the 'vast beast' comes, the sun god will rise. It's kept vague on whether it means Nika come to fight Nidhogg, or if they would join forces.
Hopefully the latter.
