Marsh Madness Moderate 7

There's something in the swamp. How the party finds out, or why they care, has a few options: a bounty from the locals for the kobolds who keep coming out of the swamp and stealing their livestock; an unusual and concerning trend of traders and travelers going missing to the east; the local merchant's guild wants to clean out the swamp in order to make trade routes go through more quickly. Either way, the party knows that there's something going on, and they want to find out what.

The "what" is Avindrax. Avindrax is a young black dragon very well adapted to fighting on its home turf. If Avindrax can be lured or forced into fighting outside of its lair it becomes a trivial encounter for a 7th level party. The lair is made up of a series of twisting interconnected tunnels filled with murky acidic water. Any PC attempting to follow the dragon into its lair must make a DC 20(trained) survival check to navigate correctly. Additionally they take 2d6 points of acid damage per round(This ignores the 5 resistance to acid normally granted by water).

Statistics for a young black dragon in Pathfinder 2e can be found here. Additionally, Avindrax has the following ability:

3-actions Harassing Gasp:
Avindrax may stride up to its speed, attack with its breath weapon, and finally strike an additional time to dive back into its lair.

Tactics:

Avindrax will attempt to use it’s Harassing Gasp to harry foes from a distance. Once pursued into its lair it will attempt to evade enemies using it’s superior swim speed, stinking cloud, and invisibility while letting the acidic waters wear the enemy down before it closes in to finish them off in melee.

Additional Notes/Alterations

If you want to increase the difficulty, you can have a tribe of kobolds having worshipped the black dragons living here for centuries. Through time and arcane manipulation they have adjusted to their environment becoming amphibious and immune to acid. Two pairs of these aquatic kobold scouts can be found within the lair’s tunnels. These kobolds are an insignificant threat themselves, but will delay the PCs as best they can. This increases the encounter difficulty to severe. .