I'm def not the only person who's tried to figure out an in-universe Dethklok discography, but I feel like I haven't seen one laid out very cleanly? The timeline I've gotten so far is:
Self-titled — unambiguously the debut album, per Doomstar Requiem. Recorded/released right after Toki joins the band.
Maggot Murder Meal — released sometime prior to the series, has gone "four times diamond platinum", mentioned only in an article in "Dethwater" that Transcribeklok spotted -- Dethwater is described as a "long-delayed" followup from it.
Dethwater — released sometime prior to "Dethcomedy", again, pretty unambiguous placement, appears to be their latest album as of the end of Season 1.
The Untitled Shirtless Album — Eric von Wiechlinghammer holds this one up and refers to it as "your last album" in "Dethfashion," toward the start of Season 2. It's never as far as I know shown being recorded or released, so it's not out of the question that von Wiechlinghammer (who I think has been in prison for a bit) got the timing wrong and it predates Dethwater.
The "Black Fire Upon Us" release — Whatever album the release party is for in the Season 2 finale, referenced in "Renovationklok" by Nathan as selling "really well, at least that's what it says in the news."
Dethalbum and Dethalbum II — both of these (and Shirtless Album and Dethwater) are shown as posters at the record store in "Renovationklok". Dethalbum II could make sense as the BFUO release, since I don't think it's ever shown in the show before this point. I also don't think we see Dethalbum shown before this point either, though, and if that's right I guess they could be a combo album or have been released in reverse order for some bizarre Dethklok-y reason. (Obviously the Doylist explanation is the creators just threw in all the cover art assets they had handy, but text is text!)
Seething Vortex — the album Nathan destroys in "Prankklok", name/timing unambiguous.
Whatever album they recorded under Abigail, credits are being finalized in "Dethdinner" before everything goes to hell.
So the minimum possible number of referenced albums is 6: Dethklok (recorded/released before the series), assume the shirtless album is Maggot Murder Meal (also pre-series), Dethwater (early Season 1), assume the BFOU release is a Dethalbum I/II combo (end of Season 2), Seething Vortex (early Season 4), and the final album (S4).
Maximum possible number is 9: Dethklok and Maggot Murder Meal (both pre-series), Dethwater (S1), Shirtless Album (S2), Dethalbum and Dethalbum II (unknown release dates), a non-Dethalbum BFUO release (S2 finale), Seething Vortex (S4), and the final album (S4). (Plus obviously anything that's just never been mentioned in the series at all.)
