[quote=@ReusableSword]
[@Zeroth]
quick question, would choosing dusk vision take up the empty skill slot Agar chose for his last level or will that still be open for one of the harpy skills?
[/quote]

It would take up the Empty Skill Slot. For those who already have full Skill Slots, it could either replace an existing skill, or you could wait until you've unlocked another slot to select it.

The "level up choice" list is cycling, in a way, so that new options are added onto previously unselected options up until a certain point. Because Dusk Vision is an Orc Inheritance Skill (something they learn naturally over time) it won't disappear from the list for a long while yet.