The Eternal Palace raid gets you the opportunity to obtain the achievement Glory of the Eternal Raider. You need to run this raid in Normal difficulty or higher.
Requirements include the completion of eight achievements:
You and What Army? (You need to defeat Abyssal Commander Sivara while all three of her lieutenants are alive and engaged in the fight*)
Intro the Marine Biology (You need to defeat the Blackwater Behemoth after collecting 50 samples of sea life from within the Darkest Depths*)
If It Pleases the Court (You need to perform various emotes to earn Queen Azshara's Favor, then defeat The Queen's Court*)
Lactose Intolerant (You need to defeat Za'qul after killing ten Twinklehoof Bovine*)
Fun Run (You need to defeat Radiance of Azshara after running 6 consecutive complete laps around her arena without falling into the water*)
Simple Geometry (You need to defeat Lady Ashvane after having each cast of Arcing Azerite pass through her*)
A Smack of Jellyfish (You need to defeat Orgozoa in the Hatchery after incubating a baby Zoatroid*)
The Best of Us (You need to defeat Queen Azshara with one player still alive who is currently affected by Essence of Azeroth*
Here you can buy "Glory of the Eternal Raider" for EU or US Servers. Also you'll get guide for completing "Glory of the Eternal Raider" and can help your friends with these hard quests.
It is a rather harder that it may seem, and we are there for you to do your game process easier.
Rewards include the achievement Glory of the Eternal Palace Raider, epic mount Azshari Bloatray; also you have an opportunity to obtain gear and gold.