Perhaps a few months late for anyone here to care, but...in-house development tool Torchlight II GUTS releasedhttp://www.torchlight2game.com/news/2013/04/01/guts/
GUTS is our in-house development tool. It lets you modify almost everything about Torchlight II, from item and skill balance, to level layouts, animations, quests, and much more. GUTS mods can be shared with your friends, and multiplayer games using mods can be found in the modded games lobby. In addition, A new launcher lets you customize which mods are currently active.
When playing modded games, you can view your mod history, any previously played mods, and the impact disabling mods may have on your character.
We've also added a special tool to GUTS designed to convert pre-GUTS mods into the official mod format, with an eye toward making the transition much easier for our ambitious early modders.
We've tried to make the process as seamless as possible, with a focus on allowing modded multiplayer games with a minimum of fuss.
New Content for Everyone
We've been working on lots of new content! Here is a taste of what awaits you ...
The NetherRealm tileset - new NetherRealm dungeons can be found via portals throughout the world
New armor sets
New pets - including the Headcrab!
New endgame map content
Additional dungeons can be found throughout the overworld in New Game Plus modes