There is the eagle at the top of the tree and also a small hawk. Yveltal is the Hawk, and Ho-Oh is the eagle and the eagles rival is Nidhogg at the bottom of the Yggdrasil. Guess what? Ho-Oh is the rainbow Pokémon and Necrozma is the Prism one. There is a third creature, the Ragnarok Squirrel. This is the Pokémon Light Trio, Rainbow (Ho-Oh Form), Prism (Necrozma Form), Shadow (Marshadow Form)