First, you will need to purchase DOOM Eternal by April 3. If you don't then you miss out on the chance to snag the game, which was one of the Nintendo 64's most prized titles.
The other catch is that DOOM 64 is not available on Stadia yet. According to Google's Stadia Twitter page, DOOM 64 won't be hitting the platform until later this Spring. Google has since deleted that Tweet for whatever reason, but it was accompanied by the image below that showcases the promotion.
DOOM 64 on Stadia comes alongside extra goodies
DOOM 64 seems to be just one of the perks if you purchase DOOM Eternal on Stadia by the required date to get this promotional offer.
Though technically the other perk is just part of the game bundle that you buy. For $60, players will get the DOOM Eternal game plus the Rip And Tear Pack, which comes with the Doot Revenant Skin, a bonus campaign master level, and the throwback shotgun weapon skin.
These three items will be available with the game as soon as you buy it. And only DOOM 64 will be on standby. Releasing DOOM 64 later in the year is a slightly odd move. Even if it is just later this Spring.
The game was a free promotional gift for anyone that pre-ordered DOOM Eternal on any other platform it is being sold. And it was available right at launch.
Did Google pull the trigger early?
While it seems that DOOM 64 on Stadia is a guarantee at this point, Google may have pulled the trigger early on announcing it as a promotional offer.
That is the only logical explanation for deleting the tweet that confirmed it as a perk. Save for maybe Google deciding to change the end date for when you need to buy DOOM Eternal to get it, and needing a new promotional image to go along with that.
The good news is that Stadia owners who wanted DOOM 64 are getting their wish. It's just a matter of when the game will actually arrive and letting the players know.
For now though, DOOM fans who also own Stadia can sink their teeth into the latest title in the series. Which has already been getting excellent reviews and is sure to provide more than enough content till the N64 title comes out.