The Golden Bell. Dark Lands, #4

She's a genius inventor hunted for a secret that could change everything. He's the guardian determined to keep her safe-even from herself. Rain Miller has been running for her life since her father's brutal murder. Half-human and brilliant, she's invented a device powerful enough to start wars-or end them. When the Black Charmers finally capture her, she knows her secrets will die with her. Until Fallon crashes through the walls to save her.
The ex-ambassador and shapeshifter guardian doesn't just rescue Rain-he claims guardianship over her and drags her through a portal to the Dark Lands for her own protection. Fallon expects obedience. Rain gives him defiance, because she didn't survive a year on the run by trusting powerful men, no matter how attractive they are. Fallon never planned on wanting the woman he's sworn to protect. But between Rain's panic around his shapeshifter guards, her habit of leaping off cliffs, and her alarming talent for building weapons, keeping her alive becomes a full-time job.
Falling for her wasn't part of the plan. When Rain's invention draws a murderer inside the council itself, Fallon realizes the greatest danger isn't the enemies hunting her-it's her determination to face them alone. To save her, he'll have to convince the most independent woman he's ever met that letting someone stand beside you isn't weakness. It's courage. A brilliant inventor. A protective guardian.
And a deadly secret that could destroy them both. A slow burn, not explicit, romantic fantasy.