| -100% on Forgotten hero upkeep.
An Era IV technology exclusive to the Forgotten which reduces the upkeep of Forgotten heroes by 100%, making them free to maintain. Note that this only applies to heroes that are themselves Forgotten, not heroes of other factions that are owned by the Forgotten. It is unlocked by completing Chapter 8 of the Forgotten faction quest.
With the arts of infiltration near perfected, agents posted to enemy cities need little time to become extremely effective, having an almost instinctive grasp for who wields power - and who is vulnerable.