The condition of the coven restricted Abel from unleashing his powers. The chains tied around him to immobilize his movements were just added heaviness. For a normal person, those chains could completely stop someone's movements.
In other words, despite the restraints and the conditions of the coven, Abel was still stronger than an average pureblooded vampire to be able to move around. Still, he had always trusted his gut instincts that tonight's coven would be different.
The coven wouldn't just kill him or attempt to force him into an eternal slumber. The night council had gotten a hold of a divine weapon; a weapon that could highly kill him. Hence, Abel had to find a way to survive since he couldn't die — not now that he found someone whom he wanted to cherish for as long as he could.
That was when Abel found a loophole while watching Sunny eat.