allanlim: So for the campaign, I got the amulet and release the barbarian but I didn't get the option to ally with the orc?
Is it because you need to have an evil alignment before that option is available?
If your alignment is neutral or good, you won't get that option to get permanent alliance with orc?
After you killed the Barbarian you will get his amulet.
If you investigate the amulet you will have several options, don't throw it away ;)...don't release the energy,...but do some "research" until you know that it is some kind of prison sealed by a powerful spell.
Then you should get the option to lift the spell and destroy the prison, you might have to talk to Zarr or one of the other Astrallords, then finish a turn and talk to them again.
After you released the "God of War" you have to talk with him until he accept that he's in your debt, then he should declare that his children will fight for you from now on as a gift and at the next shard you should be able to build the Ork-buildings. If you talk to him you have to be aggressive and warlike..to impress him..without angering him to much ;)