Contract: Phantom of the Trade Route - Velen
Quest Giver: Refugee
Other Requirements: N/A
There are three different ways for you to start this quest, the two most common are by speaking with the refugee in Benek or finding the caravan along the road. You could also start this quest by finding the Refugees in the cave as well while exploring.
Depending on how you got this quest, scroll down to the part that is most relevant for you. Starting at the beginning; after speaking to the Refugee in Benek you'll want to travel south to the quest marker on your map/compass. At this location you will want to examine the claw marks on the rock, foot prints and smashed wine barrel.
Geralt will use the scent from the wine barrel to track the Refugees back to the cave. Speak with them inside to update your quest and learn more about the beast that attacked them. The next location you'll have to visit is a bit southeast of you, use my map below or your map for additional guidance.
Aside from the two Refugees there is still quite a bit for you to find in this cave - search it before leaving! Much of this cave will be empty for you as it's part of the final Hearts of Stone quest, Whatsoever A Man Soweth.
To reach the Wyverns that you need to fight for this quest you will need to leave the cave and climb up the hill until you make it to the two Monster Nests to the east. Here you'll find two Wyverns which you'll need to defeat to call out the Royal Wyvern. Once the two regular Wyverns are dead destroy the Monster Nests and you'll get the Royal Wyvern to come down and attack you.
Wyvern Weaknesses: Golden Oriole (Potion), Grapeshot (Bomb), Draconid Oil and Aard