Long and Winding Road

Putting the ettins behind you, the party regains the road and continues on their way toward Aronsburg. Soon, the road begins descending back down the ridge toward the river cutting through the valley below. The trip down is arduous and difficult. The slope is steep and the road cuts back and forth making its way down.
After several hours on the dusty road, you finally begin to move across grassy meadows with small shrubs and trees dotting the hillside. The road begins to run down toward the lake in the distance, slowly converging with the river at a point five miles upstream from the lake. The swamp stretches back from the lake for miles along this shore, so that every step forward leads you closer to the marshy lowlands near the mouth of the river.
There are small clusters of trees and forest along the river and across the road where there is a danger of attack from bandits. These bandits can be anything from gangs of orcish goblinoids to rogue adventurers and miners looking for a more direct acquisition of gold.
As the party nears one of these copses of wood through which the road runs, they are attacked by a pair of wyverns (have the party roll perception/wilderness checks against stealth checks by the wyverns to determine whether they get a surprise attack or not). The wyverns will swoop down on the party to attack them, forcing them to decide on whether to fight or take shelter under the cover of the trees.
Hiding in the woods, waiting to ambush them as they pass through the dense canopy, is a band of 6 hobgoblins, led by two captains and a warlord. They are waiting, concealed in the woods (3 hobgoblins in trees with javelins), to jump the party as they pass through. If the wyverns drive the party into the woods, they will spring their attack early.
If the party remains in the open to fight the wyverns, the warlord will send three of the hobgoblins and one captain out to engage them while they are distracted with the wyverns. The other captain, the warlord, and the three hobgoblins in the trees will wait for the wyverns to finish with the characters or be driven off before openly attacking the party. Frankly, they are afraid of the wyverns.
Once everyone has been dealt with, the party can find a wagon of mining supplies - mostly ore and broken tools - that the hobgoblins captured during a recent ambush. There are two mules harnessed to the wagon, which are a little skittish at first, but can be calmed quickly if anyone has animal handling (DC12). Others can try by making the same skill check at disadvantage.
Further search will reveal a badly injured driver crawling toward the river. She is beyond healing, but holds out long enough to tell you that the wagon is headed to Martin's Trading Post, and to beg you to deliver it for her. Martin will pay them 200 gp for safely delivering the ore. She gives you an amulet she is wearing to show him in order to collect the payment. It has a silver chain, with an emerald set in the amulet, which is also silver. Before she dies, she tells you it is a family heirloom that she would like you to have.
Detect Magic or a successful DC25 Arcana check reveal it has magical properties...