Act 5 Quest 2: Rescue on Mount Arreat - Diablo 2
Quest Location: Frigid Highlands
Quest NPC: Qual-Kehk
Quest Goal: Rescue 15 Barbarian Mercenaries
Reward: Can Hire Barbarian Mercenaries; Ral Ort and Tal High Runes
You'll begin this quest the moment you enter the Frigid Highlands. All you have to do for this quest is to run around Frigid Highlands and free the Barbarians that are being held in cages... apparently against their will. Smash open the door to their cage and they will use their own Scroll of Town Portal to go back to town. If it weren't for you smashing that gate, they'd surely have perished.
There are a total of 3 groups of Barbarians you have to rescue, each a group of 5. Usually you will find two groups of them close together and the third one really far away. Sometimes the two groups close together are near the Frigid Highlands Waypoint and sometimes they're closer to the Arreat Plateau zone. The Barbarian enclosures have a unique icon on the map, use my screenshot below to see what it is.
Once you've freed all three groups all that's left is to speak with Qual-Kehk to get your reward (3 High Runes and the ability to hire Barbarian Mercenaries). Qual Kehk gives you the Ral, Ort and Tal High Runes which can be placed into a Shield to make the Ancient's Pledge Rune Word.