Ellis' contract was selected by the Diamondbacks on Friday, Zach Buchanan of The Athletic reports.
The 25-year-old doesn't have any noteworthy tool beyond his plus raw power, but he's performed well at the Triple-A level this season, hitting .286/.396/.554 with 13 homers in 65 games for Reno. He's primarily played third base, with the occasional start at first and second.