Soareon is the Flying type evolution form of Eevee.
Evolving Eevee into Soareon is quite easy. First, find a Pretty Wing. Give it to Eevee to hold before leveling it up. After leveling up even by 1 level, it should evolve before learning Gust on evolution. At Level 9, it will learn Wing Attack, etc. The most powerful move is Hurricane which is learnt at Level 45.
It can be found in Kalos and onwards. Wild Soareons are extremely rare and have a 0.0000000012% chance of spawning in places Eevees can be found in.