In the world of The Last of Us, September 26 is known as Outbreak Day. It's the day that, in the fiction, the Cordyceps virus reached "critical mass," signalling tough times ahead for humanity.

Developer Naughty Dog is celebrating the occasion this year with a number of activities. First, a new sale will run on the PlayStation Store which will see The Last of Us Remastered, the Left Behind standalone expansion, and "select" multiplayer add-ons discounted by a "significant" level. An Outbreak Day PS4 theme will also be made available. These one-week offers do not appear to have been made available yet, but that's no surprise given that the PlayStation Store doesn't usually refresh until Tuesday.

Additionally, Last of Us apparel and accessories are discounted by 20 percent from the PlayStation Gear Store.

In other Outbreak Day news, Naughty Dog announced it has partnered with poster and apparel company Mondo for a stunning-looking limited edition poster based on The Last of Us. Here it is:

You have artist Kevin Tong to thank for the design, which he worked on alongside Naughty Dog, according to a post on the game's blog today.

The poster goes on sale today at 10 AM PT / 1 PM ET from MondoTees.com. Naughty Dog warns that quantities are limited, so you may want to act quickly. Each poster is hand numbered and signed by Tong.

The Last of Us was originally released in June 2013 for PlayStation 3 to critical acclaim. The remastered version was released for PlayStation 4 in July 2014.

A sequel could be in development, but nothing has been confirmed. The Last of Us is also being made into a movie, but it has not progressed in years.