Altaria-Mega @ Altarianite  
Ability: Pixilate  
EVs: 252 Atk / 4 Def / 252 Spe  
Adamant / Jolly Nature  
- Swords Dance / Dragon Dance  
- Extreme Speed  
- Earthquake  
- Dragon Hammer
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Optional Move(s):
- Head Charge  
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Altaria-Mega @ Altarianite  
Ability: Pixilate  
EVs: 252 HP / 252 Def / 4 SpD  
Bold Nature  
IVs: 0 Atk  
- Boomburst  
- Roost  
- Rapid Spin
- Heal Bell / Toxic
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Optional Move(s):
- Haze
- Glare
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Overview:
Mega Altaria carves itself a couple of niche that can be worth using for some teams. Offensively, a Pixilate boosted Extreme Speed has no immunities, something most users don't have and access to Swords Dance and a great coverage in Earthquake makes it a decent sweeper. Defensively, its unique typing lets it check Marshadow, Zygarde-Complete and is one of few pokemon that can reliably handled Zekrom. Its useful utility moves in Heal Bell and the unblockable Rapid Spin lets it further support its teammates. However, Mega Altaria still struggles breaking through Fairy resist such as Primal Groudon, Necrozma-Dusk-Mane and Ho-oh due to having enough bulk to survive a boosted coverage move or even avoids 2HKO from unboosted hit.