Gula's Archaeological Dig is a location in the Mardaneus Plaza district of Aleroth that is accessible during the events of Divinity II: Flames of Vengeance. It can be entered through a trapdoor south of the Circle of Trust Inn, next to the plaza's waypoint shrine. (Note: In Divinity II: Ego Draconis the entrance to Gula's Archaeological Dig is selectable but locked, without a key to be found. Even if unlocked using the game's console commands, attempting to enter does nothing.)
The dig site was originally excavated by Sir Gula, in search of a valuable troll artifact. It was later used by the healer Heleon, who found that the humidity level within is perfect for brewing his potent Heleon Potions. He has recently fled the site, because it has become infested with undead creatures. He still has the key ("Heleon's Cellar Key") needed to unlock the trapdoor. It can be obtained by speaking with him on Lanilor Lane and agreeing to perform the quest Herbal Medicine.
The undead you face at the dig site are level 36, and for the most part, are encountered in groups of only two or three at a time. Upon entering, you'll find the first Heleon Potion on a ledge to your left (south). Take it, then proceed west descend the staircase which curves to the south. At the bottom of the stairs, smash the crates and urns in the corner where the passage turns westward again, to reveal a Troll Door Key.
Proceed west until you reach a fork with some undead enemies, where you can either head south, or continue west. Grab the second Heleon potion on the ledge, then go south, following the corridor as it curves west. You'll come across a locked Troll Door. Open it with the key you've previously acquired, and loot the chest ahead. Smash the urns here to find a second Troll Door Key, then return to the fork.
Open the locked Troll Door to the west, and press forward, killing the undead. Take the third Heleon Potion on the ledge to your right (north) just before the unlocked Troll Door. Open it, and you'll encounter more undead. Once they are killed, note the locked chest along the north wall, which requires level 7 lockpicking skill to unlock. Nearby you'll find Heleon's Log on a table, which explains why he choose to brew his potions here.
Follow along the north wall, heading west. There is an unlocked chest containing random loot, and the fourth Heleon Potion in the northwest corner. Head back towards the door, and take the fifth and final Heleon Potion from the desk. Now that you have them all, you can give them to Heleon to complete Herbal Medicine, or if Heleon was mindread earlier, you also have the option of bringing them to Bernard at the Healers' House to reveal his deceit (perhaps a just decision, considering that he kept the recipe a secret when it may have helped save many more lives if shared) for the quest A Fraud a Day.... A third option is to forgo completing either quest, using them yourself (they are functionally identical to Potions of Ultimate Rejuvenation).
You'll notice two troll statues and pedestals on southern side of this room. The pedestal in the southwest belongs to Queen Ormhildr, where you'll need to return Queen Ormhildr's Cup for the quest The Blighted Beaker given by Najaad. The pedestal in the southeast belongs to King Bragi, and is the one you're looking for to return the Golden Plate of King Bragi for the quest Fat Chance assigned by Sir Gula.
- Undead minions (level 36)
- The Blighted Beaker – Return the cup to Queen Ormhildr's pedestal
- Fat Chance – Return the golden plate to King Bragi's pedestal
- Herbal Medicine – Find the five Heleon Potions and give them to Heleon
- A Fraud a Day... – Find the five Heleon Potions and give them to Bernard
- Heleon Potion (5×)
- Heleon's Log (Books in westernmost room)
- Troll Door Key (2×)
- Random Loot (3× chests)
Click images to enlarge.