The Dragonborn Goddess
The Goddess of the dragonborn is known by many names in many versions of reality. In this universe she is the mother of dragons and the dragonborn. She is Takhisis, the five headed dragon. Her single motivation is the dominance of all life. To that end, she drives her favorite children, the dragonborn, to subjugate all other races. On her home world she was successful in her quest for dominance. The dragonborn destroyed all other civilizations and enslaved their peoples. Takhisis dominance of her world extended into the realms of the immortals. She destroyed her rival gods to reign supreme.
Her thirst for dominance drove her to search for new conquests. She gave her dragonborn followers the ability to leave their home world and cross the voids to reach other worlds. Normally the guardian spirit of a world would never allow beings from another to enter its realm and Takhisis could not intervene as she would be repelled by the presence of another spirit. Somehow, she has discovered a way to negate the repelling power and assault the guardian spirits directly. In this way she has already spread her influence to several new worlds, each time increasing her power as her followers destroy or enslave the native beings. While her dragonborn army assaults the physical realm, she attacks the guardian spirit. Once the guardian spirits are defeated, she is free to enter the physical realm to complete her utter dominance of the mortal beings. With each successive victory, she grows more powerful and her next conquest grows easier.