Defender

With her headquarters buried in rock, her resources are scarce. But Mary needs to stop the vengeful alien demi-god, Sever, before he murders the man she loves -- and before his prison of a forcefield spreads around the globe. 

But saving the world isn't a solo business, and Mary -- along with the whole league -- will need to let go of her past grudges if she wants to rescue the future. 

Defender is the concluding volume in the League of Independent Operatives superhero saga.