Figured I'd post some sort of list now. I've done my best to describe them and put timings in for most of them.
"Inside the Hourglass" - main riff/chorus riff.
No brainer here really. Heavy, catchy, melodic.
"A Sorrow to Kill" - 4:25 - 5:03
Absolute beast of a riff.
"A Sorrow to Kill" - 6:30 - 6:54
Very cool Opeth-esque riff (but better than theirs, obviously

).
"Asylum" - 3:45 - 4:02
My least favourite song of the album, but this riff is killer.
"Temptation" - 3:25 - 4:40
I love the way this riff and the drumming contrast with the vocals and keyboards, fantastic stuff.
"Blood" - main riff
I remember Lee describing this riff being a beast to play. Definately worth all that effort.
"Dreadful Angel" - main/verse riff
Heavy, driving riff.
"Phantoms" - 5:25 - 5:37
I'm running out of adjectives. You should know how good these riffs are.
"Born of Ashes" - 2:18 - 2:34 (pre chorus riff)
My favourite piece of music from To-Mera. Just incredible riffing combined with the drumming/vocals/keys etc.
"Born of Ashes" - chorus riff (aka riff after the above)
An awesome riff to follow up and awesome riff.