This is because along with the typical bug fixes and other adjustments, it also unlocks all of the game's multiplayer DLC.
The new progression system changes how players unlock demons, guns, equipment, and even customisation options.
The update will also introduce a brand new multiplayer progression system that will replace the previous random unlock scheme with a system that unlocks equipment when hitting specific levels. Runes are persistent abilities included in a loadout that, unlike Hack Modules, don't expire and don't need to be activated.
On top of that, all players' multiplayer levels have been reset back to 0, but "veteran players will have the option to reset their unlock progression and experience the new progression system fresh, or retain all of their existing guns, equipment, demons and customization options that they've acquired or purchased while unlocking some of the new items in the revised progression system". The free weekend comes with access to two levels of DOOM's campaign, Arcade Mode and unlimited access in multiplayer and SnapMap modes. The update's full patch notes can be seen on the official Doom community forums here.
"We're confident new and veteran players alike will enjoy the control and predictability in this new multiplayer progression system", game director Marty Stratton said on the Bethesda Blog.
Interested in trying out Doom for free?
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Large publications such as The New York Times and The Washington Post already employ similar limited paywalls on their websites. Facebook has tried a variety of different money making methods, but later on this year, we'll see it try something new.
The death screen is getting an overhaul as well, now calling out how you were killed, not just who killed you.
All of the information on Update 6.66 can be found here, while Doom itself is available now on PS4, Xbox One and PC.
DOOM was one of the biggest FPS (first person shooter) titles of 2016, thanks to its high octane combat and focus on retro style gameplay. DOOM will also be discounted through this period to just $14.99, which appears to be the lowest it's been price so far (digitally, at least).
Free Update 6.66 will release globally on July 19, 2017, prior to our Doom Free Trials Weekend (details below).
Another weekend, another free Xbox One game to play for Xbox Live members. Any progression earned in the free trial carries over to a full purchase.