Mundanus Imperium is not a well-known band. They only released one album and one EP, but vocalist Jorn Lande is a well-known singer in several groups such as Masterplan, Yngwie Malmsteen, and his solo project. Despite Jorn's involvement, he is not the driving force behind the band. The band is a project for Lars Wiik and Bent Holm who created this dark progressive metal band.
Mundanus Imperium was formerly known as Nattefall, a group with only one demo out. So, even in their former incarnation they were not terribly productive.
The band sounds a bit like a more symphonic version of Symphony X. Of course Jorn is a perfect vocalist for a symphonic metal band, with a big powerful tenor, and the vocals are a strong point for the band. But the symphonic elements, delivered by keyboards and synthesizers are the most noteworthy aspect. Oftentimes, it sounds as if the songwriters were classically-trained composers rather than metal musicians. The symphonic elements really shine through on instrumental "Beyond the Earthly", which sounds less like a metal song and more like an orchestral piece.
The lyrics get a little cheesy at times. They are devoted mostly toward space and science fiction, taking things a bit too far with the ridiculous "Starwars". Despite this, the vocal talent of Jorn Lande helps make up for some of these odd moments.
I really do not know why Mundanus Imperium disappeared. Perhaps it was due to Jorn's involvement in other projects, but not likely because this is not his band.