An Ohio man named Larry Dean Harmon will serve three years in prison and forfeit more than $400 million worth of cryptocurrency and other assets, the Department of Justice announced on Friday. Harmon was indicted in 2020 on money laundering conspiracy charges related to Helix, a darkweb cryptocurrency “mixer” service he ran.

Also known as crypto “tumbling,” services like Helix are designed to hide cryptocurrency transactions — often for illegal drugs — and the identity of people involved. From 2014 to 2017, Harmon processed more than 350,000 Bitcoin (about $311 million USD at the time) in such transactions, according to the DOJ’s announcement.

Harmon, who pleaded guilty to conspiracy to commit money laundering in August 2021, will be on the hook for three years of supervised release after serving his prison sentence. He also received a $311,145,854 forfeiture money judgment.

He faced a possible 20 years in prison, but the judge in the case gave him a more lenient sentence after he helped with multiple other investigations, as The Wall Street Journal notes. That reportedly included his testimony in the trial of Roman Sterlingov, who ran another crypto mixer called Bitcoin Fog.