"Defendants reproduce, distribute, monetize, and offer for download thousands of unauthorized copeis of Nintendo's video games. This includes games for nearly every video game system Nintendo has ever produced including hundreds of games for its recently released Nintendo Switch," the lawsuit states.
The site is ROMUniverse, and according to the lawsuit, it offers a premium membership priced at $30 per year for unlimited access to unfettered downloads, with no ads. This is not advertised up front on the website, though the paid subscription option is presumably offered after registering an account.
"Hundreds of thousands of Nintendo games have been illegally downloaded through the website including nearly 300,000 downloads of copies of pirated Nintendo Switch games and more than 500,000 copies of pirated Nintendo 3DS games," the lawsuit states.
ROMUniverse boasts 375,000 members and 60,000 ROMS. According to the lawsuit, the site attracted nearly 400,000 visitors in March 2019 alone, with a "significant portion" of the traffic generated by interest in piracy-related keywords pertaining to the Switch and 3DS.
Nintendo also takes issue with the site displaying images and original box art of its games. The lawsuit wants up to $2 million for each instance of trademark infringement, and up to $150,000 for each copyright infringement. That could potentially result in a massive judgement against the site.