Biography
Mortem was a Norwegian death metal band formed in 1987 and composed of Steinar "Sverd" (guitar), Jan "Hellhammer" (drums) and Marius Vold (vocals). Mortem released the "Slow Death" EP as a demo cassette, and later as a 7" EP on the French underground label Putrefaction Records.
It's not correct to say that Mortem became Arcturus, as Mortem continued for a long time after Arcturus was formed, with loads of different members within their ranks. Mortem even reformed in the mid-nineties with a new line-up.
Biography text from Last.fm, available under CC BY-SA.