King Arthur: The Druids

Summary pulled directly from Steam - Some text may only be applicable to Steam platform

Wales is the beautiful and fiercely independent realm of tribal lords, wizards, and dragons that slumber beneath the roots of Snowdonia. It’s new leader, King Ryons used to be the most dangerous warlord of the land. He wants to restore the power of the Old Faith in Britannia and he always reaches his goals.
Bow down before the gods of the ancients. Fear the creatures coming back from the twilight and respect the ways of the druids. And follow the warrior-king, who will conquer Britannia.
This expansion is the twin of King Arthur - The Saxons, offering a wide array of new content (i.e. beasts and other monsters) as well as a brand new campaign. The economic system of the base game has been redesigned for a totally new campaign structure. The player will now be able to play in a sandbox mode as the champion of the Old Faith. There is also a complex diplomatic system where campaign winning conditions can be set by the player in an open, non-linear gameplay environment.

Features

New campaign (Welsh Kingdom)
30+ hours gameplay
Free, sandbox gameplay. The objectives are strategic goals, not compulsory plot lines
Complex diplomacy system with all kings and rulers involved including: the Marauders, The Outlaws, the Sidhe courts, the high priests and some of the noble ladies as well.
Adjustable options for the campaigns: the player can set the level of the AI aggression or the importance of magic, etc.
Four new, unique heroes
Three new special units
Three new units
Ten new hero skills
Two new unit skills
20+ unique artifacts (including ten sets)
20+ unique diplomatic and battle quests.