There's no hiding a leak of yesterday's grand scale. There comes a point where it's just easier to admit defeat than try and hide what is painfully obvious. In the case of THQNordic, Darksiders III is official - and there's preliminary system requirements to prove it.
The first two Darksiders titles were relatively easy to run while being fairly pleasing on the eyes. Stylised in such a way that made each game look fantastic while actually being relatively easy on resources meant they'd both stand the test of time and reach a wide audience. Darksiders III looks to use a similar method.
Through that, the initial system requirements paint a pretty picture. Issued onto a fresh Steam page that will act as a placeholder until the game's rough 2018 release, they're merely the basic minimum requirements that 'can and will' change as the game enters the post-production polish and optimisation cycle. They could go up - they could go down. We won't know for sure until the few weeks leading to its release, most likely.
Darksiders 3 System Requirements
Somehow, the most notable mention here looks to be the storage required to house the game on your system. 15GB by today's standard either means there's some light asset wizadry going on here or we're voice of much in the way of audio - like voice acting.
Of course, the game won't be finished for some time. There's likely still a lot left to create and implement at this point, so we expect that to grow to at least 25GB in due time.