High on Fire founding member and drummer Des Kensel is leaving the band after 21 years. As Metal Sucks points out, this news follows a pair of May shows that Des was absent from; Nick Parks of Gaytheist filled in for him. Des shared the news in a post to his Instagram, where he writes:

As a founding member of High On Fire, I feel blessed to have spent the last 21 years traveling around the world pursuing my childhood dream to write and play music. After eight albums, countless tours, and a Grammy win, I am very thankful for what we have been able to accomplish as a band.
Being a full time professional musician can have its challenges. One gets through those challenges with patience, hard work and perseverance. After much consideration, it is time for me to announce that I will no longer be performing with High On Fire. I will now be focusing on new opportunities and spending time with my family.
I would like to sincerely thank all of our fans for your support throughout the years. Without you, none of this would have been possible.
Lastly, I would like to wish my band-mates the best of luck in the future.
Des Kensel.

The other members of High on Fire have yet to release a statement of their own. They just announced a tour with Power Trip, Devil Master, and Creeping Death, scheduled to start in November, and they're on the lineup of Psycho Las Vegas in August. The new tour announcement follows two recently cancelled tours due to Mike Pike's medical issues. Matt (who's also in Sleep) recently reportedly had gear stolen too. Let's hope things start looking up for High On Fire in the near future!