Legacy from The Power of Six is not a person, per se, but rather what the children of the Garde (from Lorien) call their abilties. These abilities were gifted to them by each of the nine (and later we find out there were ten) elders on Lorien. This will give them additional abilities on top of what they would have already been born with. It is hoped that they will be able to use these legacy gifts/abilities to take back their home planet from the Mogs.