Jed MacKay 
Magic the Gathering [PDF ebook] 

Across the vast Multiverse, those gifted with a "spark" can tap into the raw power of Magic and travel across realms – they are Planeswalkers, and they are being targeted. When coordinated assassination attempts on Guildmasters Ral Zarek, Vraska, and Kaya rock the city of Ravnica leaving Jace Beleren’s life hanging in the balance, a fuse is lit that threatens not just these three Guilds, but the entire plane of Ravnica. With tensions already high in the city as a comet slowly approaches, the cabal of Planeswalkers will race against time to discover who is behind the attacks, leading them to the only Planeswalker who survived through the Ice Age of Dominaria and discovering who and what lies entombed in the comet’s icy core…