At least five bands have gone by the name of Memento Mori:

1)Memento Mori was a Swedish doom metal band with power metal influences. The band was founded by Messiah Marcolin and Mike Wead in 1992 after Messiah left Candlemass. The sound can be described as a mixture between Messiah's former band and Wead's other band Hexenhaus. After two albums Messiah however called it quits and the third album was sung by a different singer. For the fourth album, Messiah returned. After that album, the band broke up. All albums have been released by Black Mark. (from their wikipedia entry)

2)Memento Mori was a band from Livingston, New Jersey, that can roughly be described as experimental indie rock. The group released one album, entitled "Is One Worth The Other?", in 2004, and broke up shortly after. The drummer, Christopher Han, went on to form Agents and Reactants. The other four members now play in The Amateur Photography.

3)Memento Mori was an experimental industrial band from Socorro, New Mexico. They released three albums from 1989-1992 on Aural Mural Records.

4)Ex-members of Cobra Kai, Sutek Conspiracy and Scrotum Grinder. Metal tinged hardcore with the most scathing female vocals on the planet. Brutal. This CD has the songs from the 12", split 7" with Kylesa and four unreleased songs. Includes 12 page lyric/photo booklet.

5)Another Swedish band (from Eskilstuna) with singer Tom Holmlund and on guitar George Németh. Started 1979 and ended 1990. Link http://user.tninet.se/~lob316g/band/memento.html (Only information in Swedish)