Mamoswine @ Life Orb/Leftovers
Role: Physical Sweeper
Trait: Thick Fat
Nature: Brave (+Atk, - Spd)
EVs: 252 Atk / 156 SDef/ 100 Def
Moveset:
- Avalanche
- Earthquake
- Rock Slide
- Curse
Explanation: Avalanche and Earthquake are for STAB and abuses Mamoswine's high Atk stat. Given its nature and Curse (ups Atk and Def stats, lowers Spd), Mamoswine is highly likely to attack later, meaning Avalanche's power will double to 120. Rock Slide is for coverage against Flying, Bug, Fire and Ice. The EVs spread is so since Curse already ups Def so I decide to give more EVs to its (lower) SDef.
Alternatively:
Mamoswine @ Life Orb/Leftovers
Role: Physical Sweeper
Trait: Snow Cloak
Nature: Adamant (+Atk, - SAtk)
EVs: 252 Atk/ 252 Spd/ 4 HP
Moveset:
- Ice Shard
- Earthquake/Bulldoze
- Rock Tomb/Rock Slide
- Amnesia
Explanation: Unless the opponent uses a priority damaging move as well, Ice Shard will hit first, making up for Mamoswine's lackluster Spd. Earthquake is high power and STAB, but if you wish to, Bulldoze, although significantly lower power, lowers the target's Spd by one stage. Rock Tomb for lower power but lowers opponent's Spd by on stage or Rock Slide for higher power and chance to flinch. Amnesia is to raise Mamoswine's dreary SDef stat.