There is an audible wrongness to Portal, the mangled English of songtitles alone suggesting the band are living in their own Lovecraftian world. Over four albums we've slowly grown used to the demented, otherworldly death metal that Portal don't so much create as channel from an alternate dimension, culminating in 2013's Vexovoid which caged the sprawling, mumbling chaos into something approaching song structures. The band are almost an ancient terror that has taken human form, and is finally learning to mimic normality in a way that's recognisable, albeit still clearly not belonging in its skin. It makes sense then that full-length number five, ION, changes the formula a little more with a step sideways from its predecessor, not just with a clearer (yet still low-fi) production that strips back the murky gloom that so enhanced past albums but with more avant-garde sensibility that introduces more depth to the ambient side of the Portal sound and even threatens to remove the horror aspect altogether at moments.

ION does not change Portal's sound so much as their genre, moving from pure horror to science fiction. Intro Nth is a muffled ambient piece with scraping noises and a strange digital roar in the background, completely wrongfooting you when first track proper Esp Ion Age kicks in with guitar riffs that are almost crackling like the simple but evocative cover art and blastbeats, vocalist The Curator's croaked whispering madness in your ears. It's more like Krallice than what we've come to expect from Portal, albeit Krallice if their bodies were possessed by horrific alien parasites. Ending suddenly and leading straight into Husk, after a brief burst of ambience it's back to those riffs, taking the lead more and more over the other instruments until on Phreqs there is an amazing moment where they're left alone to carry the track for just a little bit too long, tension building before the drums fade back in as the guitars shrilly riff away oblivious like a particularly mad jazz band warming up. Somehow it works as death metal, albeit clearly no death metal you've ever heard before!

It's not the only time on the album that Portal push at the limits of what we understand death metal to be. Listen to the opening sawing racket of the terrifying Crones, which is soon drowned out by the clamouring guitars - neither that, nor the ensuing black metal-infused battering really counts as death metal, even with The Curator's repeated gasps of "pray for sickness" atop it all. Another example is Spores, which is two and a half minutes of cacophony the likes of which I haven't heard since early Carcass, although this is blunt noise, with what could be riffs and voices buried in a blizzard of sound. Obviously much will rely on the listener's tastes, and to what extent you allow your imagination to colour in the shapes that a band forms, but where past Portal albums evoked Lovecraftian visions, this is more like listening to a man dying from being exposed to the void of space. It happened throughout the album for me; for instance, the almost industrial percussive slams of Phathom brought to mind a lost soul futilely hammering at the side of a spaceship. The connecting thread is, of course, Lovecraft's frequent trope of men being driven insane by horrors that their minds were incapable of processing, the aftermath of which is a perfect interpretation for nine-minute finale Olde Guarde, which deconstructs into eerie vocal moans before a hellish choir strikes up beneath a crackly old veneer, as if being played on a turntable in an abandoned asylum. After five albums we've grown used to the band's shtick, but that such references come to mind still says a lot about the power of Portal's music.