During Act Three, Hartlebury can be found on the bridge leading through Baldur's Gate[note 1], watching over the queue of residents trying to make their way into the Upper City. With her fellow Fists having received orders to not let anyone into the Upper City, she is among those trying to keep the queue orderly and prevent anyone from entering.
Once all Netherstones are acquired by the party, and should they return to Baldur's Gate, three infected refugees by the queue will proceed to transform into Mind Flayers and attack the nearby party. Hartlebury will be Surprised, but will fight alongside the party. Once the Mind Flayers are dead, she and all the Fists around will run away to warn their superiors, before completely vanishing from the game once far enough.
Shoot a green arrow that bursts in a spray of acid. Deals 4d4Acid damage immediately and 2d4Acid damage at the end of the target's next turn.
If the spell misses, the target still takes half the initial damage, but no damage at the end of its next turn.
If it is higher level than the spell slot you used to Counterspell, you must make a check using your spellcasting ability[See Notes] to prevent it. The check's difficulty is equal to 10 plus the level of the spell you are trying to counter.