The Lord of the Rings Online: Siege of Mirkwood is the second retail expansion pack for the MMORPG The Lord of the Rings Online: Shadows of Angmar and was released on December 1, 2009 in North America and December 3, 2009 in Europe. Unlike the first expansion this edition was only available via a web based download.
The expansion added the southern region of Mirkwood. The game's level cap has been increased to level 65, and the expansion included the conclusion to Volume II of the epic storyline. It also introduced a new "skirmish" system that allows for repeatable, randomised and scalable combat based instances that can be accessed from anywhere in the game world for 1, 3, 6 and 12 players and new 3, 6 and 12 player private instances that take place in Dol Guldur proper.
Source: Wikipedia, "The Lord of the Rings Online: Siege of Mirkwood", available under the CC-BY-SA License.