Last year, Crusader Kings II went global modification of the Guardians of Azeroth, which changes the game universe of World of Warcraft. The map was replaced on Azeroth, in the factions there were elves, orcs and other races, and also added the magic and other features of the game Blizzard.
Recently, the mod developers have announced the release of a major update that adds a lot of innovations. Among the main functions are allocated to the disease (devouring plague and frost fever), the immortality of the night elves (while Nordrassil is destroyed), and the World Tree.
With regard to the latter, they can plant the druids, and after a siege the opponents will be able to burn them.
Find out all the details of the patch can be separate article. The gamemode itself is available at Moddb.