Start Idril's rescue, or at least reunion, by following Baranor to the local arena, and killing or dominating the caragor.
Next you have to defeat a wave of ologs, maybe using the caragor you just acquired.
After them come a wave of 'pit-fighters,' but all just no-name grunts.
And finally a captain to lay low.
When he's defeated, it's time for a few sweet words with Idril (though not for you), and mission completion.