The Orcs occupying Tharbad have been attacking travellers and destroying or stealing their goods. Turn around is fair play, as they say.
'I am so angry that our trip to Tharbad has been ruined by those awful Orcs! I wish I could walk right into their camps and destroy things of theirs, just like they did to us a few nights ago! But I am no match for them, alas.
'You, however, could enact my revenge, could you not? If you come across any of their stashes of weapons, destroy them! Hahah! That will teach them!'
Melia has asked you to destroy caches of Orc weapons in Tharbad.
Tharbad is in southern Cardolan.
You should let Melia know that you have enacted her revenge upon the Orcs.
Melia is at Stonecrop Encampment, north-east of Tharbad.