A fleet of warships invades the Weydana system, and the PCs must launch their own armada to withstand the attack! When Watcher Krulveth, the leader of the invading forces, wishes to speak to the PCs in person, they must decide whether to meet her in good faith or expect an ambush. But stopping Krulveth and her armada doesn't mean the system is completely safe. A wandering pulsar approaches, and with it, an uncaring extraplanar entity that floods the system with deadly radiation. Every living person in the Weydana system counts on the PCs to protect them from this terrible threat! The Culling Shadow, an adventure for four 11th-level characters, concludes the Horizons of the Vast Adventure Path, a six-part, bimonthly campaign in which the heroes are at the forefront of exploring and charting a world filled with mystery.