I’ve done 3 PVP battles, and I’m using 3rd gen arkadions, and the other players are using arks that’s I’ve never seen or heard of? Like gyphorn or something (a bird ark) and I’ve never seen it? Are they fusion arks or something?
Gryphon is a reward from the arena. Some of the arks you have never seen are either probably fusions or egg-only arks. If you have not finished the game yet, I prefer you do to get some of the other fusions.
Cheers bluejay 
I’ll do that then,
Mostly are Also egg exclusives
It’s also possible to get Gryphon from an egg. That happened to me on my other save slot