I'm pretty sure that's
More spoilers about the scene as I remember it:
Spoiler:
I think the heroes (Loren and Matt? With some of the visitors from our world?) were on their way to (or from?) the dwarwes to check out their version of the warning stone *) when they came across the giants. A group of svart alfar were keeping the giants imprisoned because they couldn't kill them directly. The giants were powerful, but pacifists, and the smoke was magical in some way, so they couldn't get past it.
After the heroes freed the giants (probably by killing the svart alfar), the giants promised to show up in the final battle against Sauron, um, I mean Maugrim, I think? They wouldn't fight, but they would help by magically healing the people fighting against him.
*) Sigh, a magical warning which only works as long as
all the components in the chain are maintained properly, and which doesn't have a way to signal "Out of order, please turn your magical fire off and on again", is a pretty stupid warning system
