Whoops, there are thirteen Forsaken. But there is one called Ba'lal, very similar to Bah'laal...
The majority of them are past heroes of the previous wheel. Kind of like the Myth world's cycle and those who were 'turned from the light' such as Soulblighter, the Deceiver and (insert last here).
The Aiel remind me of the fir'Bolg. Not quite human, with different skills which set them apart, plus they never really liked humanity.
The land to the north (where the Aiel live) was once fertile and is now barren. Kinda like the Barrier.
LR