Horde Hall of Fame for Sepulcher of the First Ones Closing at the End of This Reset

wowhead.com:

The Hall of Fame for Sepulcher of the First Ones should be closing at the end of the current reset (May 17th for NA and May 18th for EU) for the Horde faction as 100 Horde Guilds have defeated Mythic Jailer. For the rest of this lockout, Horde guilds should still be able to obtain Hall of Fame: The Jailer (Horde). After this lockout, the achievement will only be available for Alliance guilds, with only 9 slots claimed. Note that these dates haven't been confirmed by Blizzard, but are based on previous Hall of Fames. Horde Sepulcher of the First Ones Hall of Fame

The guilds that have achieved the Top 100 Worldwide kills of Mythic: The Jailer on each faction are awarded the Hall of Fame: The Jailer (Horde) achievement. Any player who obtains Mythic: The Jailer and is in one of these guilds will be able to use the title! After this weekly lockout, which ends on May 17th for NA and May 18th for EU, the Horde Hall of Fame will be closed and no more entries will be accepted. Alliance guilds will continue to be able to enter the Hall of Fame. When both the Horde and Alliance Hall of Fames have been completed, Mythic Sepulcher of the First Ones will become available for cross-realm groups.

For Shadowlands, Sepulcher of the First Ones has been the longest Hall of Fame to fill out, taking 45 days since the world first Mythic Jailer kill. Below you can see the time each of the previous Horde Hall of Fames took to fill up. If you count from the opening of the Mythic difficulty, the World First kill took 18 days, with the Horde Hall of Fame taking 63 days to fill up.