Battling the Imprisoned is similar to the first time around. As before, you want to kill it by repeatedly shoving the stone spike into its head three times (nine hits) before it reaches the temple.
You can achieve this by either cutting off the boss’s eight toes from its feet, or by using the whirlwinds or a jump from a higher ledge to reach the boss’s head.
With the latter method, you may be shaken off, but, if not, you have a pretty open shot at the spike. To drive the spike in, use vertical slices appropriate to the situation.
However, there is another thing the boss can do other than step on you or use its foot shockwaves (which can be guarded with a shield). It can climb walls. That is partly why Groose’s catapult is here.
Whenever the Imprisoned tries to climb a wall, if possible, press Up and aim to launch a Bomb at it and stun it. You aim with the Wii Remote, use the Control Stick to move along the wooden track, and press A to shoot.
If you ever hit the Imprisoned with a catapulted Bomb, it is stunned. That is where my strategy comes into play.
Rather than get repeatedly battered by the boss’s feet, go up to a ledge higher than it and stay above its head. Do not yet jump on its head. Wait for Groose to stun it with a Bomb, then jump on the head and do some up-down vertical strikes.
Repeat this process another two times. Note that, after being hit with the spike thrice, the boss will shake you off (when applicable) and then usually do a forward charge. Avoid it and follow it, then repeat.