Blissey @ Shed Shell
Ability: Natural Cure
EVs: 252 HP / 4 Def / 252 SpD  
IVs: 0 Atk / 30 Def
Calm Nature
- Softboiled
- Heal Bell
- Whirlwind / Transform  
- Wish / Seismic Toss / Toxic
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Optional Move(s):
- Super Fang
- Glare
- Rapid Spin
Optional EV/IV(s):
- 4 HP / 252 Def / 252 SpD Bold / Calm Nature
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Overview:
Blissey's high HP and Special Defense stat allows it to check some special attackers. It seperates itself from Chansey by entirely avoid trappers such as Mega Gengar and Gothitelle. However, it has lower bulk in comparison to Eviolite Chansey, meaning special attacks like Modest Primal Kyogre's Water Spout and +2 Xerneas' Focus Blast can 2HKO it whereas Chansey can avoid it and is prone to any kinds of physical attacks.