Nightborn Lou Anders by Lou Anders instant download after payment.

For fans of Lloyd Alexander and Brandon Mull comes Book 2 in the acclaimed Thrones and Bones fantasy-adventure trilogy that began with Frostborn.
Karn Korlundsson is a gamer. Not a riddle solver. But in order to rescue his best friend, Thianna Frostborn, he will need to travel to the faraway city of Castlebriar (by wyvern), learn how to play a new board game called Charioteers (not a problem), decipher the Riddle of the Horn, and tangle with mysterious elves.
Meet Desstra. She's in training to join the Underhand—the elite agents of the dark elves. When she crosses paths with Karn, she is not all that she appears to be.
Everyone is chasing after the horn of Osius, an ancient artifact with the power to change the world. The lengths to which Karn will go in the name of friendship will be sorely tested. Who knew that solving a riddle could be so deadly?
The novel includes instructions for playing the board game...