Dialga @ Life Orb / Shuca Berry / Adamant Orb
Ability: Pressure  
EVs: 96 HP / 252 SpA / 160 Spe  
Modest Nature  
- Doom Desire  
- Spacial Rend  
- Fire Blast
- Dragon Tail / Stealth Rock  
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Optional Move(s):
- Toxic
- King's Shield  
- Thunder  
Optional Item(s):
- Steelium Z
- Leftovers
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Overview:
Dialga possesses a good offensive presence coming from its high special attack stat and access to Doom Desire. In addition, its good defensive typing and natural bulk makes it hard to take down. Unfortunately, Dialga is unable to check Xerneas unlike other Steel-Types, which forces its team to pack an answer to it and potentially stack weaknesses to the team. Its average speed forces it to move last and take a hit, which can lead to being worn down throughout the match due to lack of reliable recovery option.