Yea, that part of the system is REALLY confusing. They tried to tie "gets special abilities other characters don't have" to the system for it ... Feats ... that was in place. So, being able to get the juice from their WoL, a character will have a feat.
But then they make it confusing by not tying the feat to the normal feat system.
You get the feat as a "Bonus Feat" when you complete the proper ritual. The Least Ritual can be performed at any level from 5th level on. You find out what it is, pay the cost, perform the ritual in game terms and then you GET the Least Legacy bonus feat. Then having the feat allows you to use the abilities.
They could have seriously just dropped that middle step and told people that after performing the ritual, you get to use the Least abilities of the weapon.
Additionally, the actual levels of what make up Least/Lesser/Greater Legacy Abilities isn't well called out in the text and there's absolutely no way to tell from looking at the weapon entries themselves ... they tell you what the rituals are supposed to be, but not where and when.
As far as I can tell, from building an item, the breakdown is like this:
Least Legacy
5th-9th level
Lesser Legacy
10th-16th level
Greater Legacy
17th-20th level
You can perform the legacy ritual at the lowest level you get the abilities, and don't get those abilities until you do. So if you turn 10th level, that ability is a Lesser Legacy Ability ... but you don't get it until you perform the Lesser Legacy Ritual for that weapon.
I like the book. Good idea. The execution leaves something to be desired in places, but still fun.
--fje