"Tyranny of Dragons" is a Dungeons & Dragons campaign storyline that was released in 2014. It consists of two adventure modules: "Hoard of the Dragon Queen" and "The Rise of Tiamat."

The storyline follows a group of adventurers who must stop a group of evil dragons known as the Cult of the Dragon from obtaining a hoard of magical artifacts and using them to resurrect the dragon goddess Tiamat. The cult has been collecting these artifacts and using them to power a spell that will bring Tiamat back to the mortal realm.

The adventurers must journey to various locations, including the town of Greenest and the city of Elturel, where they will encounter a variety of allies and enemies, including a group of mercenaries hired by the cult, a group of rebels fighting against the cult, and a group of dwarves who have their own grudge against the dragons.

Ultimately, the players must find a way to stop the cult and prevent Tiamat from being resurrected, either by disrupting the spell or by defeating the dragons and their allies. The storyline includes a variety of challenges for the players to overcome, including battles against dragons and other monsters, puzzles to solve, and moral dilemmas to confront.