The catalyst of events that has led to the current horror in Ravnica is the felicity triskelion. A reality warping artifact of eldritch proportions, which has been released to the greater world after being stolen by the Dimir mind mage Rogad Nar. After investigation and intrigue amongst the various guilds of Ravnica a chain of events left the triskelion in the wrong hands and ultimate horror has been released upon all in Ravnica.
The Thousand Year Storm is part eight of the Secrets of the Triskelion campaign for use with Guildmasters' Guide to Ravnica and is set in various locations in the Tenth District. The Thousand Year Storm represents the bad ending to the campaign. The players have failed, the triskelion has been opened, and Primal Horrors heve been released on Ravnica. Only a slim chance exists that the day can still be saved, if the party is brave, smart, and lucky enough.
- from the publisher's blurb