Possibly the best album he has ever made. It's the most consistent and works beautifully as a whole. While I enjoy most of his other work, to me this is his most important piece.
Deathspell Omega - Si Monvmentvm Reqvires, Circvmspice
Tough call, as I find Fas - Ite, Maledicti, In Ignem Aeternum and Paracletus equally important. I think that out of those three, this would be the album I'd want to listen to the most often.
Obtained Enslavement - Soulblight
Quite possibly the hardest choice of the three. I debated showcasing the fact that I do indeed have a really broad taste of music, by including Tom Waits, The Killimanjaro Dark Jazz Orchestra, Scriabin - The Poem of Ecstacy, Man Man, Krang, Virus or even some Aesop Rock, but in the end I decided it came down to either this album or Lux Occulta - The Mother and The Enemy. And out of those two, Soulblight just stands out more even though it is far more straight forward.