This mission will take you through the Watchweald Temple. This is a medium sized dungeon with two floors. You'll mainly be facing off against Nether creatures here, although a few Named's will naturally make an appearance as well. These foes are notable for their powerful, lumbering smash attacks. These moves will take off a good chunk of your life bar if they connect, but they're pretty clearly telegraphed and thus easy enough to avoid once you figure out their various tells. At times, you can even dash around to the enemy's rear and attack while they recover from the slow and powerful melee blow.
Punch, shoot and blast your way through the bulk of the dungeon, keeping a careful eye on your health and mana as you do so. As you progress, it can get kind of easy to be backed into a corner what with the wealth of enemies occupying the screen at any given time. Keep your wits about you and remember that you can easily dodge most of the attacks thrown your way, and you'll be fine.
When you reach the Grand Regent's chamber, remember to fill up all of your health and mana before entering. If you are able, you should also transform your pet into a Vampiric Spider at this point. The Vampiric Spider, for those who don't know, can sap health from enemies and give it right back to you. You will want to make use of this for the tough fight ahead.
As you first enter the room, you will see tentacles pop up in the pit in the center of the room. Stay away from the edges of the pit no matter what. If you get too close, the tentacles will pounce on you and damage you heavily. Simply wait for the Regent to emerge and float over to solid ground to attack you. At this point, you can really open up on the Regent. The boss doesn't have a ton of health, so whittling him down should be a simple matter of repeatedly hitting him with all of your strongest attacks. Keeping your health up is the only concern in this section, and the reason that we suggest using Vampiric gear or pets when possible.
After a minute or so of battle, the Regent will summon minions to his side. When this happens, take your focus off of the Regent and put it squarely onto the minions. You don't want them chipping away at your health even as you are fighting off the advances of the Regent. Take care of the minions, remembering to stay far away from the central pit, and then return your attentions tothe Regent.
As the Regent falls, a Guardian will appear. Speak with the Guardian and the quest will end. This will also open up a portal back to town. Don't head through the portal just yet, though, as there is plenty of treasure to be looted from the Regent's chamber. Be sure that you grab the nearby chest before going back to town!