Catalastor

As iy was recommended by other users , you can use Chaos/esencia gacha for superpowers/traits/characteristics. When to find new charecters / anime I would recomend first of all to check all titles possesed by big companies and write them down in the note book and e.t.c . After that using any wiki to find more details about these one, you can go and check less famous/popular one titles. Also you can similar aproach to a western cartoon companies like Nickelodeon , but with films i don't know how to work with. (You can correct me , if anything wrong , cuase english my third language)

i search in google and it said that Rei is popular japanese name

Yourmungard is the serpent that devours the world in the North Mythology, and Amarok (that's the correct name ) is the giant wolf, the guardian of order and balance of nature in Inuit mythology.

Why ? I didn't see it so much or just don't remember , or maybe you are talking about Goru Goru no mi ( Logia: thunder)

Fenrir, Surtur, Fafnir, Yuormungard and Amarak ( that all mythichal creatures)