The Death Plateau quest is necessary. High agility is recommended as it saves you from having to run past a couple of ranging trolls. Protect from melee is also recommended as you have to beat a troll well over level 100 (he hits you with what looks like half a tree and knocks you back while doing damage, he can be ranged/maged from some spots though). And you have to run past several trolls during the quest. At the end, when freeing the recruit, make sure that you also free mad Eadgar or you'll have trouble later on when you want to do Eadgar's Ruse. When you have to beat the Troll General: Two can be ranged/maged and one of these can also be hallied.
You reward is a law talisman and the ability to craft law runes. You can only have one law talisman at a time but if you turn your original into a tiara and then go back you'll say you lost it get another one.