The 'Fall of the Space Core, Vol. 1' sees a Space Core from Portal 2 follow users around in the open-world role-playing game.
Valve jokingly said that the patch will "fix" the problem that prolific voice actor Nolan North, who voiced the Space Cores in Portal 2, had no involvement in Skyrim.
"Also, since Skyrim was the only major release of 2011 without Nolan North in it, you should consider this mod a patch to fix that problem," read a statement.
"You can now feel free to include Skyrim in the 'Nolan North' section of your video game library, which is to say, your video game library."
The mod was released to celebrate the opening of the Steam Workshop, which allows users to browse and download the latest mods, complete with ratings and automatic downloads.
Also released was a Creation Kit which grants players access to the toolset Bethesda used to develop the game, enabling the creation of user-generated content.
The service began yesterday with the High Resolution Texture Pack, but has expanded to over 240 mods in its first day. Mods range from the useful - offering new locations and abilities - to the bizarre, such as the 'Posh Mudcrabs' mod that gives all mudcrab enemies a monocle and top hat.
The Elder Scrolls V: Skyrim was released for PC, PlayStation 3 and Xbox 360 in November. It was recently named as the fastest-selling PC game on digital distribution service Steam.
> Read our review of The Elder Scrolls V: Skyrim
> Read our review of Portal 2
Watch a video outlining Skyrim's Creation Kit and Skyrim Workshop below: