For this fight, just increase Mag's stats with Linear or Gre's skills, then pummel the boss with Mag's Hammer or Hand parts. Blocker likes to afflict your characters with status ailments, so use items (or Linear's skills) to cure and heal the party. Not all that hard.
It has about 3000HP, drops Upgrade Kit.
Moves: Smoke Bomb,
Chest Beam,
Spiral Upper.
