I'm pretty sure most of the chords are of the same shape- the type akerfeldt uses a lot with the A string and the B string fingerpicked simultaneously.
The model is that you hold down the A string one fret higher than the B string (I'm not really into technical jargon so this might not make sense!)
But its used in songs like-
A fair Judgement
Stairway to Heaven (obviously not opeth)
but yeah, i think that's the model for most of the fingerpicked chords of the song
A single pair of hands at work is worth more than a billion clasped in prayer