Tremble by Mary E. Twomey

When October Grace begins reaping souls, she doesn’t think life can get much worse. Mason and Von have their work cut out for them, trying to keep the council members from abducting October. Everyone wants to get their hands on the sagrado stone they need to heal their broken homelands. Now, with all the nations vying for their piece of the stone to heal their land, October doesn’t know who to trust. Her attraction to Mason proves problematic when a simple kiss threatens to splinter apart the trust in their platonic threesome.

After accidentally killing off an entire race in Terraway, October isn’t sure who the biggest monsters are – the ones trying to work her into an early grave, or the one she fears she’s becoming herself.