Opeth songs has almost always several instrumental parts built up by (i.e.) a riff that is repeated exactly 4 times.
(Then comes perhaps another riff, chord sequence or vocal part... again often repeated the same number of times.)
This is VERY typical of Opeth!
Later (newer) album songs has (partly) the same structure, but with the excellent difference that things are slightly changed, or parts are added, during the four repetitions.
The more varied these riffs/sequences are, the more you can appreciate that they are repeated four times.
But many early Opeth songs tend to become slightly booring when you sort of KNOW what'll come...