Pretty new to competitive battling, but I have been thinking of a defensive core consisting of Mandibuzz and Magnezone:
Mandibuzz @ Leftovers
Trait: Overcoat
EVs: 248 HP / 252 Def / 10 SpDef
Impish Nature
-Foul Play
-Taunt
-Roost
-Defog/Toxic
Magnezone @ Assault Vest
Trait: Magnet Pull
EVs...