That is odd, I can not find the 4e version of the boon in the manuscript.
However, the 3e version granted the ability to shake of a mental attack.. which can be done very easily in 4e depending on how generous you want to be with it. I would rule that the boon is an ability to make a save against the dominated, dazed, and stun conditions, usable once per encounter as a minor action.
That would be a solid boon to have!