She found the old tome behind a new wall in the family shrine. It'd been bricked in. Hidden. 

Of course Hisame can hardly resist such a delightful temptation.

She skims through the book, pauses, then reads more thoroughly, a grin growing on her face.

Maybe it's nonsense. Sacrifices and blood and dark chants all for show.

But it was hidden for a reason. And maybe it's something more.

Maybe her way out of this damn Hidden Village.

Decima is good at stealth, and good at killing, no matter how Konoha keeps trying to shackle her. Finding an 'innocent' no one will miss in the next twenty four hours isn't actually that hard.

The symbols are fun to paint - she's never been allowed to play with blood properly - and she lights the sacred incense, carefully recites the chants, maintains the proper atmosphere within the shrine's sanctuary - 

And tries to summon a god.