There is a concept within spirituality called 'The Divine Feminine & Divine Masculine.'
Where the second symbolizes strength, logic, action, and protection; the first is the force that leads him, guides him, nurtures him, and heals him of all lingering trauma. (Although it is important to note that he must do the same for her.)
Through the discovery of these roles and interactions, either by chanced meeting or magical circumstances, the pair in question may attain a relationship that is deeper and more meaningful than any other, with no chance for replication or imitation.
Embodying the divine feminine and masculine concepts are not necessarily a requirement for successful relationships, and is completely subjective as roles can often be fluid between couples.
However, attainment is a surefire way to cement the symbolization of unity.
And Abaddon knew for sure as he looked at the woman in bed with him that he had reached that true unity.