Hey guys, I just figured out how to get Fenrawr, the secret Pokemon with number #719.

First, you need to beat the game, E4 and such, get the National dex, blabla. Then catch all birds (they'll be beyond the dex) and complete your dex until you have all 150 "regular" slots filled (so 450 Pokemon in your regional dexes).

Then, you will need to beat the E4 one hundred more times. Then go to one of the forests where you can catch Flabébés. Run around a lot until you meet a Flabébé (it's very rare so take your time) which looks like a shiny, but has a strange "aura" around it (the game will also indicate it with a special text). Make sure you catch it, if you make it faint or let it escape you have to delete your game and start all over again.

Then go and beat the E4 another time, but with only that Flabébé, your starter and your legendary and nothing else and you have to release all your other Pokemon. You will face Az again, who will comment and recognize his friend again instantly. He will flip his shit and attack you with mega formes of his original Pokemon and Flabébé will now be in his team. It's the hardest battle in all games, but if you win, then Az will recognize your strength and reveal himself as the old King of Kalos. He thinks you're worthy and will give you the Mirror Stone.

Now go to the reflection cave and Fenrawr will show up. It's level 100, you can only catch it with the Master ball and its only move is "Death Ice Beam" which kills your Pokemon instantly.