Make your group then begin heading west. I'm sad that you don't get to control Cairne yet but at least he is with you. You will be attacked by a group of centaurs before too long and they must be dispatched to protect the caravan. That's how this mission is going to go. Those centaurs don't want you to succeed. The caravan will follow you so don't get too far ahead of it. You'll come to a spot where you can choose the northern or western path. Take the western one and kill everything here to get a scroll of healing and a potion of mana (destroy the huts to get one of those). Be warned that the caravan may be attacked while you are doing so. As a matter of fact there's never any guarantee that the caravan won't be attacked.

Now go back and take the northern path. Note that if your beasts are damaged they can be healed quickly with the talismen of healing you have. The path heads east and you should again follow it. Take out any centaurs you come across before the caravan reaches you. Now you can see that you are clearly heading toward the first oasis which is apparently a fountain of healing, which is good.

You may be ambushed a couple times but when you finally make it, you'll be greeted by three grunts who will join your party, great! Northeast of here is a group of murlocs. When you destroy them eliminate the eastern huts to find a figurine which will give you +1 intelligence when held, which is good for Thrall.

Now head to the west and you'll encounter some more centaurs, one of which drops a claws of attack +3 which is, again, good for Thrall (but not great). You'll see that the path snakes around to the east. Follow it and you'll encounter many more centaurs on your way. At the end of the eastern path you'll find a merchant where you can purchase scrolls of healing and three raiders will join you. The raiders can use the ensnare ability to immobilize an enemy unit. Use this on big centaurs while you take out the small ones (keep your distance from the immobilized one).

Take Thrall to the center of the caravan and use a scroll of healing if you need to. If not, you could use the talismen to heal the party. Now head north. Where *sigh* the path again snakes to the east. There are harpies here and if you've lost your headhunters, Thrall will have to do a lot himself. Or so you might think! Use the raiders' ensnare ability to bring the bitches to the ground and slaughter them. The big harpy is the most problematic. It can use this tornado skill which immobilizes one of YOUR units. Hopefully you get her to the ground and kill her before she wreaks too much havoc upon your party. I'll admit I did lose a couple units here. When she's killed she drops a totem of might which increases str +1 when carried. Not so great for Thrall but we'll hold onto it to give it to Cairne when we have control of him, right?

Just north of here is the second oasis and upon reaching it you will recieve three catapaults. Make them into a second group to control them more efficiently. I recommend you save your game at this point. Now the location of the third oasis is revealed, and to begin our perilous journey to it, we should head west. The path diverges to the north and you should be wary of the two towers here. Use the catapaults to destroy them. A little further north are a third and fourth. Again, use the catapaults. Past that there is When this battle is over if any of your units are damaged you should take them to the fountain to heal as, it's so close.

East of here is a very perilous thing that should almost be considered a side quest. I used the three casts of lightning shield on three melee units and headed in. There is a HUGE creature which can severely damage and stun all of your melee fighters with one ability (like thunder clap). You aren't required to do this but if you can beat him he drops a pendant of energy. This adds 150 mana and at such an early level this is a huge bonus. Also in one of the huts is a tome of agility which you can use to add a permenant +1 agility to Thrall. My Thrall now had a full inventory of items. I dropped the strength item (sorry Cairne) and kept everything else. If you succeeded in this, congratulations! If not, sorry for you luck and try again (I did tell you to save didn't I?). But now you should head west. There is not a very long path to get to the third oasis now. Use the catapaults to destroy the towers and move slowly. I used the feral spirit spell to scout ahead (in some ways this is better than the far sight spell). I managed to reveal all the towers between the location just before the pendant of energy guy and the final oasis. Now you just need to implement that intelligence. Nothing too difficult. Even if you lost a lot of units in the previous battle. Your feral spirit should help a lot.