Canon-wise I'm unaware of any seed-kin to the Timeless and Oakvein.
Sargent hints that the imprisonment of a devout Nerull worshipper lays in Spikerift, although he never comes right out and says it.
I picked a Black Dragon, a species I usually shy away from, thinking that their powers are the type that would keep the area much like Sargent described it. Foul and Swampish.