UPDATE: In recent months a lot of Scythes of the Emperor fiction has been coming out of Black Library, check the Essential Reading Guide here.
UPDATE Sept. 2020: Laurie J Goulding recently commented the following about the Scythes History PDF back in 2011:
The Original History PDF Article:
After a few snatched moments of spare time over two months, we have both served our penance for the odd historical inaccuracies that have persisted among Scythes of the Emperor players due to our notoriety as Scythe collectors. My original Scythes history of misremembered romantiscised facts and Andrew’s own very convincing Scythes history had many believing the very characters we wrote of were in fact, GW canon!
Now, after twelve years of collecting the Scythes I think I can say, this is the most accurate history compiled to date. Fully sourced and cited from Games Workshop and affiliated publications. We have often gone with precedent facts, due to GW’s penchant for some odd revisionist time line.
Download : The Scythes of the Emperor : A Factual history [18mb PDF]
What this is not
The Scythes of the Emperor : A Factual History is not a codex or even a hobby guide. It is a several page report on the history of one of GW’s most ill-fated but resilient Chapters. Our intention is for Space Marine collectors to explore the possibility of a Scythes’ force with the confidence of knowing the background with which they get inspired is accurate and presents a myriad of possible Scythe Chapter forces fighting and surviving along the Eastern Fringe. Much like my small warband of marines and Andrew’s complete Scythe Company with Battlebarge, there are various ways to represent them in the 40k realm.
The Future
This is the first edition release, as new facts may yet come to light. We will incorporate in later editions these new addendum. If you find something we have missed, please contact us and we will cite the source and add it to the next edition with credit.
Enjoy,
Sebastian
Site owner and creator, Sebastian Stuart has been updating and maintaining the Scythes of the Emperor webpage since 1997. He is canonised as 'ForgeMaster Sebastion' by Richard Williams and LJ Goulding in the Scythes of the Emperor novels by Black Library. 
Good work on the history, very interesting.
Also good to see that you update the site and the new design is pretty cool.
Best regards a Scythes of the emperor fan :)
Hi Daniel,
Thanks, Andrew was superb in chasing down the source material. He has great access to GW literature at home and through friend in GW. I put together the artwork, proof read while we discussed some content choices, then finished by producing the PDF based on his solid research. It was a great collaboration. :)
I certainly feel we finally put the history of the Scythes right and in context for all collectors out there.
– Seb
Job well done guys. Been painting Scythes for a couple years but just found this site, looking forward to any updates.
Thanks Chris, glad you enjoyed our collaborative efforts. Apparently Andrew’s Scythes are in the latest edition of Warhammer 40k rules, which is some seriously good news and kudos to his work.
Fantastic work guys. Scythes of the Emperor have always been my favourite SM chapter; due in no small part to the excellent artwork and gameplay of the first GW product I ever owned – Advanced Space Crusade. I was wondering in all your research have you been able to shed any light on the origins of the Chapter? I have read other indirect sources citing the Scythes as a successor chapter to the Ultramarines (thus descended from Roboute Guilliman?) although this does not feel right to me.
Hi Dale,
Thanks! It was fun publishing the research that Andrew put together at GWHQ. As far as we can surmise, the closest tie in is the Ultramarines. Locale, interaction and the recent fiction wherein the Ultramarines debrief survivors and take on their suggestions. (Very circumstantial) That said, not exactly the worst chapter to be affiliated too.
Thanks for your questions and checking out the site, I’ll be updating recent work on my new Scouts (based on Adv. Space Crusade actually), should be a couple of days :) – Sebastian.
I’m confused on the timing here. This document says that Sgt Remas was part of the first fight against Hive Fleet Kraken, but his testimony is then used in the formation of the Tyrannic War Veterans, some 200 years earlier?
My reading of this (just from the 40k wikia) is that the Scythes were actively involved in the First Tyranid War against hive fleet Behemoth, and in the founding of the Tyrannic War Veterans.
This might just be poor GW editing and consistency, though?
Its a fair point; we or more so, Andrew, encountered a lot of these issues when reviewing information he was able to find with help from GW friends. The more recent Tyrannic War Veterans (last year I believe) info tends to lessen the Scythes contribution even further.