The newbie wrote:
looking back i have made good use of cave dwellers once or twice. It was in a seige game (no model cap) I used every goblin model I could muster and every orc with a few trolls thrown in. I used the trolls/orcs as a distraction at the gate whilst the goblins climbed full speed up the walls. It truely was a thing of beauty watching my 70 goblins suddenly be ontop of the walls

One Ring Rulebook, p 56: "Castle Walls may not be climbed unless a scenario specifically says otherwise. (This rule even applies to Moria Goblins - but not to large spiders such as Shelob.)"