1st thing -
thordendal dont use 8 string tat much during live performance
as seen during troy performance:
http://www.youtube.com/watch?v=fpjj29szuFo&search=meshuggah
secondly the reason they got an 8 string mainly becoz they are crazy.....hahah....nah.....because they like to tune their string damn low and every thing they do with their music according to them are just playing ard..for example their latest ep CATCH33 which was actually an experimentation not an album.....they used to have a nevborn guitar but it was tedious for them as they have to tune every time after a song and for this reason i suspect they went to approach Ibanez for help...
the nevborn guitar
# 8-string electric guitar, tuned F, Bb, Eb, Ab, Db, Gb, Bb and Eb (low to high) or to customer's specs.
# 3-piece hard rock maple, graphite reinforced through-body neck, with an ebony 24-fret fingerboard.
# Alder body with a maple top.
# Extended scale length for a clear and defined low end with superb overtones.
# Features an ABM bridge with fine-tuners, and a locking nut.
# One custom-wound Lundgren humbucking pickup. [/img]