Mega Evolution for Rayquaza revealed
Pokemon Omega Ruby & Alpha Sapphire — 13 October, 2014
Mega Rayquaza remains Dragon/Flying type but gains a brand new ability, Delta Stream, which creates a new weather condition
strong winds. Just like Desolate Land and Primordial Sea revealed previously, the strong winds summoned by Delta Stream cannot be removed by normal moves or abilities while Rayquaza stays in battle - in fact Delta Stream appears to take priority over Desolate Land and Primordial Sea.
Strong winds also reduce damage from the types Flying is normally weak to (Electric, Ice and Rock) to any Flying type Pokémon in battle.
Rayquaza also has a new move Dragon Ascent which is Flying type and apparently will be the most powerful Flying type move in existence (which currently is Sky Attack at 140 base power). Check out the official video below: