If you killed the Embeth Travelers during the quest An Amusement for the Nobles, or if you stole the prize for the competition via an [Evil] or [Chaotic] dialogue option, your sociopathic chickens will come home to roost sometime as you're exploring. While this may very well happen later during one of the numerous quests that'll pop up a month or so after finishing An Amusement for the Nobles, this encounter will be listed here for the sake of continuity.
When this encounter happens you'll be stopped by a group of armed men and women, who introduce themselves by saying "Jamel Visser sends his regards." You had to have known your murder wouldn't remain a secret - the difference between the wounds left by a wyvern and by your weapons and spells would be obvious to the trained eyes of a hunter.
If you pick the dialogue option "You and your band had best leave while you still can." you'll immediately provoke them, although their method of prosecution is a bit odd. They're not here to kill you themselves, instead they're going to let the forest judge you. If you can overcome the trial ahead, you'll earn your right to live. In this case the trial involves fighting a Ferocious Wyvern - the same beast whose trophy you deprived the Embeth Hunters of. This isn't a terribly challenging opponent, although it can attack quite fast and its attacks are venomous. Haste and Stoneskin should overpower it quite dramatically.
If you want to try to talk your way out of trouble, pick the dialogue option "Who are you and what do you want from me?", after which you'll get a variety of options. Picking the [Chaotic Neutral] or [Chaotic Evil] response will both lead to them summoning the Ferocious Wyvern, while the [Bluff 35] and [Diplomacy 35] checks both offer a chance to avoid conflict. In the case of the [Bluff] check, you need merely succeed, while with the [Diplomacy] check you'll further have to pay 3,000 GP in restitution.
Should you have not killed the Embeth Travelers during the hunt itself and merely strong-armed the prize from Jamel you'll have an optional [Diplomacy 20] dialogue option. Like the higher-difficulty [Diplomacy] check, words won't be sufficient recompense for your deeds - you'll also have to forfeit 1,000 GP or fight the Ferocious Wyvern to prove your worth.
Whether you have to fight the Ferocious Wyvern or not, after you're done paying for your crime, continue west until the path splits. At this point turn north and search a rock hidden by some bushes to find a Token of the Dryad. Not a bad trinket to pick up, all things considered.