The folks at Turbine are keeping busy. After announcing the first expansion to Dungeons & Dragons Online last week, the developer has revealed its other free-to-play MMO, Lord of the Rings Online, would also get a new expansion.

"Riders of Rohan" will allow players to "join forces to ride into the Plans of Rohan," and is set to arrive this fall. Coming with the newest LOTRO expansion is an increased level cap to 85, "iconic locations" such as Amon Hen and Fangorn Forest, and a new "Mounted Combat" system.

Riders of Rohan comes as Turbine's Lord of the Rings-themes MMO is set to celebrate its fifth anniversary. "One of our largest expansions ever, Rohan is expected to be twice the size of the recent Rise of Isengard expansion and includes the most new game systems and technology we've introduced since 2008's Mines of Moria," LOTRO executive producer Kate Paiz said in a press release announcing the expansion.

In September 2010, Lord of the Rings Online switched its business model to free-to-play. One month later, developer Turbine said that making the change helped double the game's revenue.

In the press release announcing Riders of Rohan, publisher Warner Bros. Entertainment and developer Turbine detailed new additions and changes coming in the expansion:

Experience the Riders of Rohan: Join with the Rohirrim and ride across the sprawling Plains of Rohan; witness the breaking of the Fellowship at Amon Hen; forge alliances with the Ents of Fangorn; and aid Eomer, adopted son of Théoden, as he seeks to protect his homeland from the growing Shadow.

Introducing Mounted Combat: Ride into Combat atop your loyal War-steed as you defend the people of Rohan from the forces of Isengard and Mordor. Customize your War-steed's armor and level its skills over time to aid you in mounted defense of King Theoden's lands. Mount your steed and gather your fellows to fight against Warbands, contingents of roving warg riders that have been scouted all over the Plains of Rohan! It falls to you to head off and defeat this new threat before they over take the land.

Advance to level 85: Continue your legend in the next chapter of The Lord of the Rings Online. Experience new adventures in the epic story, and gain new skills and deeds as you face new challenges on your journey to 85!