Couple of things:
First, this isn't all one quest called "Cove of Decay - Prison Break." That quest is over when the centaurs are released, and the female one tells you to see Chieftain Kraughl. At that point, you do not have the quest anymore, you've completed it.
Speaking with Kraughl, you'll get a completely new quest, "Cove of Decay - Kraughl's Request." He want's you to go out and kill Grinash, and upon returning, the quest will be complete and he will tell you to talk to Orulan.
When you speak to Orulan, you get yet another quest, called "Cove of Decay - Reforming Stormsunder." This quest is an *Access Quest*, as opposed to simply being under the Thundering Steppes heading like the previous two. From this point to the end is this quest.
So there are actually three quests here, not just one long one. I didn't know if maybe someone would want to make new entries for accuracy's and clarity's sake.