My Pet Dragon Is The Fallen Dark King

I used to be the powerful Black Dragon Monarch, but I was ambushed by my cronies. My remnant soul was reborn in a dragon egg, and I was contracted by a human girl. I awakened the Devouring and Strengthening System, and all spiritual materials and monsters can help me restore my strength. The girl bears the heavy burden of saving her sister. I accompanied her to explore secret realms and search for treasures. Along the way, I met kind-hearted people, dealt with difficult people together, collected elemental origins, recovered lost swords, gathered my strength, settled old grudges, stayed with my companions, and found our own peaceful world.