They probably used a Boss HM-2 at some point.
Damn, are you sure Tornio? The sound has been SO different from album to album - I find it genuinely unlistenable on "Resurrection," "Nightmares" just sounds like any other Tagtgren tone, and "Fathomless" is just sooooooooo middy and crunchy, I love it
Resurrection Through Carnage only used the Boss HM-2 pedal direct in, no amps at all!
Here's what Anders Nyström says: http://www.ultimatemetal.com/forum/4073981-post8.html
Posted before "The Fathomless Mystery" came out...