A good portion of the new content is going to be released today, which includes new characters, new maps, new game modes, and lots of other new goodies that can be unlocked within the game. More content will be added over the span of a few months, but the update releasing today will contain a colossal makeover to the game. The user interface will be getting a nice little re-polishing as well, and bugs and other factors will be given time to be found and squashed during this beta phase.
The game is going up for free most likely because Turtle Rock has been guilty of poorly handling the financial aspect of Evolve. The game went up for a pricey amount and added a lot of DLC that was also relatively expensive, despite claims from the company that all added downloadable components would be added free of charge. In addition, the company acknowledged the lukewarm reception the game got and the added justification that, in order to give a better game experience for the players, there would be a lot of content added to the game for no added charge.
It appears this is mostly a crisis of conscience here, since Turtle Rock didn't handle the release of Evolve very well and noted that it got pretty mixed reception from its players. After turning players upside down and shaking them for all the change in their pockets, representatives Chris Ashton and Phil Robb acknowledge that they went about this poorly. This is probably an attempt at a turn-around for them, since even newcomers will be able to join in on the experience for free.
The beta phase will launch on PC only for Stage 2. When the beta has been finished, the update will release on consoles as well. It is unknown if console players will have to pay for the update.
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