Here is the full list of all 13 Shadows Behind the Throne 2 achievements.
Enthrall or create your first agent
Win a Game
Use a vampire to drive a King, Queen, Empress or Emperor insane
Consume the last human city with the Unholy Flesh
Achieve victory without enthralling or creating any agents
Enthrall a noble with the Dark Heirophant
Have your seeker agent learn the terrible truth
Have a merchant load and sell cargo, then spend the wealth
Declare your nation to be a Dark Empire
Have a Noble's soul break due to reaching 100% shadow
Reduce the world's temperature to half what it was at the start of the game
Use a Saviour agent to stop an invasion on a nation with at least 10 locations
Reach the end of 'The Twins' Event Chain