[Yossar]

Originally posted by Curath:
I need to do some more testing on it, but Forge of the Ancients seems to halve the gem costs, NOT give 50% forge bonus. Dwarven smith with Forge Lord hammer (75% total bonus) uses 10 gems (25% of 40) for a Robe of Invulnerability.

Forge of the ancient halves the base cost before Forging and Construction bonus are taken into account. Robe of Invulnerability has a base cost of 80 gems. Half of that is 40 with the Forge of the ancients. Multiply by 0.75 for the Forge bonus and you get 10. Ta da!