Great job on Behemoth Ultimatum

DefenderThese guys are sort of like the Big Daddy's when it comes to enemy strength, watch out for them at all times.
As large and slow as these enemies are they are very strong as brute force is highly used, but most of there strength isn't there own. For the most part the shield does the work, it has a mind of its own so to speak. Since it can attack within range watch out for the shields jaws as they can cause significant damage. It's wise to always defend during this time as when you do the defender lifts his shield when you parry one of his attacks take that chance to finish it off (if at low damage), or attack from behind. One of the other more aggravating attacks is it's spin attack (reminiscent to Goofy's Tornado attack)
One other thing to note is that as good as it is close range it does have a couple long range attacks as well, making group battles tricky as not paying attention to them on the field can leave you with avoidable damage. It's two long range attacks is a slow moving Fira attack and the second is some sort of blizzara attack (a mist like projection from its shield), they're slow moving but can only be parried with a guard (square button when the ability is on) or a counter attack from close range (they do use magic at close range as well, specifically the blizzara spell).
(Partial spoiler)First encounter with these foes is a risky proposition as in the beginning of the expedition of Hollow Bastion you're physically impaired so magic is you're only option, make sure you pick up ether's and elixirs before hand to better prepare yourself. Still don't get to righteous, let Beast take care of most of the work until you get the Keyblade back.
After the events of Hollow Bastion they are less common there as the darkness has spread to other worlds so places like Traverse Towns and early levels consist of them along with the likes of other heartless from Hollow Bastion.
Item Note:There is a 5% chance of the the heartless to drop his shield as a drop item for Goofy to use in combat. Usual item drops are 40 HP balls,80 Munny, and items Elixir, Bright Crystal, and the Defender Shield.
Trivia- This heartless (like the wizard to Donald) represents the moves of ally Goofy, shield and all including stances and attack patterns.