In Lover Avenged it's detto what it is, is basicly and a part in his body that conects with the female he is having sex with but it only conects when he comes and then it releases itself after he is done. hope this help te understand it a little bit.
Being part Sympath makes Rhev an "animal" so when he's with Ehlena his "barb" engages much like a dog's when they're mating. Ever try separating two Cani when they're busy?, te can't, te have to wait it out. That's the little extra Rhev's sportin' for his shellan (good for her)