When the Sentinel’s health hits 75%, it will jump to the wall and attack from range with electric attacks. It’s best to do this from range with Fire magic or Barret’s attacks since if you get close he’ll hit you with Tail Swipe and Scorpion Strikes.
It will soon envelop itself in a shield, so you need to take out its Field Generator.
To begin with, you should use your Lightning magic to attack it since it’s weak towards that element. The Scorpion Sentinel is the first boss in the game and is actually one of the tougher ones. Assess Info: Its stagger gauge does not fill while its force field is deployed.Immunities: Poison, Silence, Sleep, Slow, Stop, Berserk, Proportional Damage.