From the Overgrown Pool area heed the following directions:
Northwest (to reach empty node, can cross river to the south)
West (path loops 180 degrees)
You probably won’t detect your destination, Three-Pine Islet, until you reach the end of the last step. Once you do, however, you’ll be able to enter.
Do so and you’ll find yourself along the southern end of the Three-Pine Islet area map, with running water to the north. Turn east and make your way to an area transition, near which you’ll find two of the beasts that plague this area - Tatzlwyrms. Cut them down and be wary of their poison, then ford the river to the north of the area transition.
Across the river you’ll find a Tatzlwyrm corpse, the site of which should encourage caution. Sure enough, pass a [Perception 18] check to spot the trap that presumably killed the monster, then disarm it [Trickery 18] so you can safely loot the beast. Loot a bit of stone near the corpse to acquire a Potion of Vanish and another Scorched Fragment of a Necklace along with some other, less interesting treasure. Be wary, however, as another trio of Tatzlwyrms lurk further north. Eradicate them and pass a [Perception 8] check to spot more treasure hidden amidst some ruins, including a Potion of Enlarge Person.
To finish this small area up, head west from these ruins to find a beached boat, near where several Tatzlwyrms are gathered. Kill them, then search the boat to discover most of the goods (besides some food) are missing. Turn south to find a hidden cache in some stonework, which includes a Potion of Cure Light Wounds.