Honestly, every time I listen to the song, I think of Watershed's booklet artwork.
Derelict Herds just completes the ensamble for me though. To me, Watershed as a whole gives me that 'trippy hippy other worldly' type feel. Every song, there's something in it that gives me that feeling. Most of Opeths albulms have a more serious feel, and kinda a exact location (ex. Still Life = Medieval Times) but Watershed is just experimental and doesn't seem to know where its at, like the albulm itself if based in a dream.
And derelict herds just makes it more dream like.
With that said, I think Opeth could have worked on the artwork with Travis a bit harder, and made the whole cd just a little more focused on this aspect, if its what Opeth were going for.