Spiderlight by Adrian Tchaikovsky

The church of Armes of the Light has long fought the forces of Darkness. And its great prophecy dictates that Dark Lord Darvezian will fall to a band of misfits armed with their wits and the Light’s blessing, and led by a priestess. But to reach the Dark Lord via the ‘spider’s path’, as the prophecy states, they’ll need a spider. They’ll discover that not even the power of sorcery can disguise the grotesque creature’s true and appalling nature, nor its unwillingness to be part of their quest.

As priestess, mage, knight, ranger, and rogue squabble their way through a journey fraught with peril, they question whether the creature called Nth is a monster, a tool or a friend. And ahead lies a mighty confrontation. If they can survive it, it will change all their worlds forever.