The successful use of the Heaven Binding Seal hinged on the marked difference in soul strength between Tang Yin and the target. That way, the target's resistance and unwillingness to be enslaved would not matter in the grand scheme of things.
However, the effectiveness of the Heaven Binding Seal relied on the substantial gap in soul strength between Tang Yin and the target. If the target possessed a much stronger soul, the Heaven Binding Seal would only work if they chose to lower their defences and willingly permit the seal to be imposed upon their soul.
Obviously, no being would want to become subservient to anyone.
