"Ontological Mysterium" is the fifth full-length album from the progressive death metal band, HORRENDOUS. It was released on August 18, 2023, by Season of Mist. HORRENDOUS started as an old-school death metal band and has been steadily getting more progressive with each release. "Ontological Mysterium" is no exception. The album opener, "The Blaze," is a short intro track. As far as intros go, this one is adequate. The vocals get lost in the guitar work but the track still sets a tone. The following track, "Chrysopoeia (The Archaeology Of Dawn)," is a perfect way to start an album. It follows the previous track without any delay and kicks the album into high gear. The lead vocals are varied but almost always of the harsh variety. The backing vocals are clean, providing an excellent counterpoint. The lead guitar solos are well-written and well-placed. The riffs, tempo changes, and overall dynamic variety remind me of BETWEEN THE BURIED AND ME even though the vocals are different styles.

"Aurora Neoterica" is a two-minute instrumental track. It has a repeating guitar theme that is decorated with some great keyboards and lead guitar parts. It is possibly the least technically demanding track on the album but fits perfectly between its surrounding tracks. "Cult Of Shaad'oah" is my current favorite track on the album. It opens with the shouted vocal, "Beat me back but I'll keep on climbing." Every time I hear that line I get excited. The same goes for the callback towards the song's end. The musicianship is top notch as the instrumentation ebbs and flows, while constantly changing and evolving. There's a shredding lead guitar solo that's also not to be missed.

"The Death Knell Ringeth" closes the album and features the same instrumental wizardry that you've come to expect by this point. The lead vocals start out sounding like a demented Dave Mustaine and proceed to get even more ravenous as the song continues. There's a great bouncy riff that gives Alex Kulick's bass guitar flourishes space to shine. It's an excellent track concluding an exceptional album. I've been a fan of HORRENDOUS ever since I first heard "Ecdysis" in 2014 and they just keep getting tighter and more impressive with every album since. I've said it before and I'll say it again, 2023 is a great year for metal.