Dungeons of Sundaria

Just adding my notes as I play through this myself, there are 4 crystals that need deactivating, each one atop a tower with a boss fight, you can find these by following the beams leading to the dome over the castle, the bosses spawn in additional enemies and lock you in to the top floor of the tower until complete, once complete press A on the crystal to deactivate. The gates on the bridges can be smashed with a spell/attack (took me forever to work this out after spending 20 mins looking for a lever). The boss is a Minotaur, the best way I found to beat him with the Wizard was to kite him around one of the columns so he couldn't charge me and generally was out of melee range. Obviously may not be the best option if you are using melee yourself but if you need some space and time to heal then it will give you a bit of breathing room rather than being smashed in the face constantly.