Jace Beleren has the power to travel between planes of the Multiverse, but with this gift comes isolation. He is one in a million. He is a planeswalker. And he is on the edge of a mystery that could alter the face of his adopted homea vast, world-wide city known as Ravnicaforever.Faced with a magical code that is built into the very foundations of the city-world itself, Jace marches into the numinous depths of Ravnica's underbelly in search of the promise of powerful magic. What he finds is perhaps more burden than boon. Once buried in past, the code resurfaces as Ravnica's power-hungry mage guilds, unbound by the Guildpact that had once maintained order, struggle for control of the plane. But in the drive for primacy, there is no neutral ground.Jace knows that he can't crack the code on his own, not while the guilds task teams of mages to unravel the mysteries, but he also knows that the danger of the quest is too great to include his friends. As the mystery begins to unravel, the choice may not be his alone.