Torchlight 2 is on sale at the moment to celebrate a large update being pushed recently.
Single Steam copy is $9.99US but there's also the Torchlight II 4-pack for $29.99US - Includes four copies of Torchlight II, send the extra copies to your friends!
The Steam page notes that "SPECIAL PROMOTION! Offer ends 9 April". I've listed the expiry here as the 10th.
Happy slash 'n' hackin'!
The new update made multiplayer worse. Only those with the exact same mods loaded will be able to see each other in the online server browser. Stick to vanilla if you want to play with randoms.