Portal and Blood of Kingu is a bit of a weird mix for a split, but I guess the occult leanings of both artists make for a thematically occlusive bargain. Portal is an Australian experimental black/death band known for obscuring and suffocating production styles, whereas Blood of Kingu is a Ukrainian black metal band with ties to Drudkh and Hate Forest via vocalist/guitarist Roman Saenko.
Portal's track is a 1999 recording from shortly after the release of their self-titled demo. If you're unfamiliar with this period, you might be surprised at the overall "death metal" feel here. The Curator's vocals are a guttural roar, not the whisper-growl of the LPs. Horror Illogium's guitars have that skittering, schizoid sound typified by Seepia (and, later, ION) rather than the outright "atmospherics" of Outre' and Vexovoid. The drum programming is not bad, but it's obvious - lots of snare hits and consistent blast-beats rather than the more spacious drumming of later releases. It's not a bad track by any means, but it is definitely early Portal - and therefore best sought out by extreme fans.
The Blood of Kingu track is a brand-new recording for the split, making the split kind of a funny case of two songs recorded 15 years apart. This is a straight-up black metal song, and with a much more bestial sound than the atmospheric black metal you might expect from Saenko's other bands or the De Occulta Philosophia LP. The bass is extremely prominent here, giving this track a bit of a death metal sound compared to the earlier LPs. This track lacks a lot of the outright esotericism or samples present in some other Blood of Kingu tracks, opening with a short dark ambient portion before launching into black/death madness. Perhaps not a mandatory listen either - but given Blood of Kingu's fairly limited discography, fans should check this one out more than Portal's side.