Once a Villain by Vanessa Len

The final book in the lauded Only a Monster trilogy is here—where the unstoppable love and high stakes of Divine Rivals meets the propulsive thrills of This Savage Song in a last-ditch, breathless race against time.

Joan has failed to stop Eleanor.

Now Eleanor rules over a cruel new timeline where monsters live openly among humans, preying on them and subjugating them.
Nick—once a hero to humans, and Joan’s first love—is tormented by the choice he made to save her over the timeline itself. And Aaron—the ruthless heir to a powerful monster family—now finds himself in a world where monsters have power beyond imagining while his feelings for Joan grow.
Wrenched between love and rivalry, the three of them must negotiate their fractured pasts to survive the new world and restore what was lost. Because only they remember that there was once a better timeline.

But how will they defeat a whole world of monsters with control over time itself?