The Spooks Destiny book 8 and I am Grimalkin book 9 by Joseph Delaney

Destiny book 8

You belong to the blade now. You'll belong to it until the day you die . . .'

Tom, the Spook's Apprentice, has travelled to Ireland, where he must tackle a group of evil mages. His dangerous mission leads him to the Destiny Blade - a sword with a dark side, and a thirst for blood. Could this new weapon give him a fighting chance against the Fiend? And dare he accept the help of Grimalkin, the terrifying witch assassin?

and 

I am Grimalkin book 9  Take note cover town check photos 

 am Grimalkin, and I have already chosen those I will kill . . .'

Grimalkin has made it her lifetime ambition to destroy the Fiend. Having assisted the Spook and his apprentice in the binding of the Fiend, she is now on the run. And her mission is deadly. She has to keep the Fiend's severed head in her possession no matter who - or what - comes after it .