Celesteela @ Leftovers / Shed Shell
Ability: Beast Boost  
EVs: 248 HP / 252 Def / 8 SpD   
Impish Nature  
- Beak Blast  
- Leech Seed / Toxic  
- Roost  
- Heavy Slam
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Optional Move(s):
- Defog 
- King's Shield
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Overview:
Celesteela's solid bulk, recovery and a great typing lets it serve as a check to Mega Salamence, Kartana and Diggersby. Its decent utility option through Beak Blast burn, Leech Seed and even Defog can help support its teammates. However, it is prone to being set-up on by bulky Substitute sweepers, which they can shut it down and uses it as a setup fodder. Due to its passiveness, it is prone to being trapped by Shadow Tag users such as Gothitelle and Mega Gengar, though the latter has to be careful as it is 2HKOed by Beak Blast and Heavy Slam.