Diablo 3 Walkthrough Part 29: Trailing the Coven

Killing Queen Araneae (Spider Queen) should provide you with good quality loot, including a bunch of purple items (magical items), and up to two yellow items (rare). Pick up the loot. Karyna tells you that you'll need the Queen's venom to dissolve these webs. Your quest tracker updates:

Trailing the Coven
Harvest the Pool of Venom in the Chamber of Queen Araneae.

Interact with the toxic pool of fuming green water,  which should be found in the same chamber where you killed the Spider Queen. Then, free Karyna with the venom.

Karyna thanks you, and wants to leave this horrible place. Your next objective is to go out into the Highlands Crossing. The exit to the Highlands Crossing is just behind the spot where Karyna as held, so take that exit (and do not go back to the beginning of the cavern). When you are outside at the Crossing, talk to Karyna. She tells you that it was terrible, being stuck in there like that. She thanks the gods that you came along. She asks what you are doing out here. You tell her you seek the man that was taken away by the Coven. Karyna says she saw them dragging someone into Leoric's Manor house; perhaps it was the man you seek. You might have a small bit of trouble reaching there, though.

Karyna is not proud of the fact, but she confesses that she stole the staff of a powerful Khazra Shaman. The shaman went mad and chased her to the caves. You can find the staff in Karyna's card in the Highlands. If you take it to the Khazra Barricade, perhaps they will let you pass.

Your task now is to find the Khazra Staff, located on Karyna's Lost Wagon in the Southern Highlands. Head down the stairs and follow the path west. Along the way, you will encounter Dark Moon Clan Warriors, so be prepared to fight.  There will also be a flying monster here, the Withermoth. There is a waypoint here in case you need to go to town to restock. Otherwise, keep going westwards. Go through a gate and cross the bridge. A Dark Moon Clan Shaman is waiting for you on the other side. After neutralizing him, continue the journey along the road.  Watch for Highland Walkers, who look like trees, but launch to attack you. Explore the Southern Highlands.

The fields of the Southern Highlands consist mostly of open areas, and they are swamped with monsters. It is easy to try and escape from one group, just to run into another group, and become surrounded and outnumbered. So try to quickly eliminate groups of monsters you encounter, and stay in a small radius while fighting. There are also elite bosses here, for example Fade, Patron of the Mad (Teleporter), as well as huge Savage Beasts (Vortex).