It was using Dragon Pulse. I can recognize the animation without even needed to see all that moonrunes. Now I remember Serebii stating that Double Chomp was a dragon type move as well, was it ever mentioned official that Double Chomp was a dragon type attack?It seems like Ononokusu was using a Dragon attack on Hihidaruma (the shade of blue/purple is characteristic of many Dragon attacks).
This doesn't mean its Dragon but it's pretty darn likely and that's what we figured anyway.
IMO, likelihood of it being a Kibago evolution is high...not that I was ever convinced otherwise.