Hey, this will be a very brief history lesson.
Just for clarification, Lordaeron is a realm with buffed encounter values (Bosses have more HP and shorter enrage timers, there is no ICC buff enabled, back then there was also no RDF and of course, no coin shop here). During the course of the realm's life, most encounters were nerfed from their original values, but the core difficulty still remains, counterpart to the retail values.
The realm first kill of Lich King 25HC was made by Horde guild <MEMORIES> in 2017 (
https://www.youtube.com/watch?v=xh_s1EktcO4&t=4s), when the encounter was nerfed from 130M HP and 13:38min enrage time to 103M HP (enrage stayed the same). As a fun fact, the very same day, their rivals Alliance guild <Archetype> also made the kill as realm second, a few hours after. After their kills, most players from the guilds stopped playing and quit the realm, thus the guilds died.
After that, two other guilds emerged, with largely new players, Alliance <After Life> and Horde <Raven> and started the ICC progression again. <After Life> killed LK 25HC as 3rd guild on the realm in 2018 (
https://www.youtube.com/watch?v=swYDlFeDx1Y&t=694s), followed by <Raven> (
https://www.youtube.com/watch?v=Z9wc5n8vEXI&t=1s) a few months after. These two guilds started farming the encounter and made significant roster changes during their years of playing, but both guilds stopped raiding years ago. <KappaXD> was the 5th overall guilds to kill LOD on this realm.
These were the last guilds that managed to kill LOD with the buffed values. After that, ICC was nerfed a lot, so other guilds managed to secure their kills and progressing ICC got way faster and easier.
Also, after about a year of ICC patch, RS was also opened, with <After Life> killing Halion 25HC as realm first (
https://www.youtube.com/watch?v=AFSsD7qCa3A&t=313s), followed by <Raven>.
This post:
http://forum.warmane.com/showthread.php?t=386015 contains the values that were in play during those times, but now most got nerfed.
Hope this was of interest. If you wanna know anything more, just hit me up!