Magearna @ Leftovers  
Ability: Soul-Heart  
EVs: 248 HP / 28 Def / 232 SpD  
Calm Nature  
IVs: 0 Atk / 29 Spe  
- Flash Cannon / Fleur Cannon 
- Heart Swap  
- Heal Bell  
- Volt Switch

Other options:
- Ok so this is the only set I have really used much with it on stall, but Magearna is still Magearna so...
- Pain Split
- Protect
- Ice Beam
- Calm Mind
- Thunder Wave
- Pretty much anything you can justify tbh...