Torchlight II is on Steam, and you can run it natively in Linux, which is very nice! But what about Torchlight I?
Even though there is a native version of the game, Steam doesn't provide it. Of course you can run the Windows version through wine, but it's always better to run a program natively.
Currently, the only way to get the native version for Linux is by purchasing it from the humblebundle.com store. You can link your copy with Steam afterwards, so you can still install the game trough Steam for Windows/Mac.
A few issues
I ran in to a few issues installing the Linux version, but was able to solve it.
When you see the message "Error: Overflow detected: Not enough space for widget." you can try running the installer with a different GUI frontend option. For example:
./Torchlight-2013-05-21.sh -f fltk
You've installed Torchlight
When you've successfully installed the game, most likely you'll notice having mouse issues. You won't be able to click on anything and your cursor might have a black outline. It's because Torchlight doesn't work well with the latest libSDL2 library, so you've to use an older version of that library.
To install these older libararies, probably the easiest way is to download them from here. Extract these files into your Torchlight/lib64 folder. You should now be able to play the game.
For more info about this solution, click the link below:
Managing Save Games
Next thing you might wanna do is using your Save Games for other devices that run Steam. Since you can't sync automatically you'll have to do this manually. The easiest way is to make a copy of your ~/.runicgames/Torchlight/Save folder, and override the folder on your other device. For Windows it's located in %APPDATA%\Roaming\runic games\torchlight\Save.
Make sure Steam Cloud is set to off. In Steam, just right click on Torchlight, go to Updates tab, and turn Steam Cloud Off. Also make sure the sync folder in Steam is removed, otherwise it will still override your Saves. The AppID of Torchlight is 41500, so you'll have to remove the \Steam\userdata\YourSteamID\41500 folder.
Don't worry about the Steam Achievements when moving Save Games around, Steam will automatically recognize them.
Well, that was it! Hopefully one day they'll fix the installer, and we don't have to mess around with library files. Then most likely the native version for Linux can also be played trough Steam.