The Kirin Tor expedition was sent to establish presence within the overgrowths of Gorgrond and create an alternate access point to Draenor since the Dark Portal was shut down, but all contact with the mages of the Violet Bluff was lost after they were overrun by the forces of Primals, led by a fearsome genesaur named Yalnu. Archmage Sol's brain has been infested by spores that turned her and most of the expedition against their allies, and a portal link to a Kirin Tor camp located at the outskirts of Stormwind City is still active, attracting the fearsome genesaur and his underlings towards Azeroth, where they can spread unchecked without their eternal enemies, the Breakers opposing them.
Dungeon Journal
After the disruption of the Dark Portal, the Kirin Tor realized that to fight the Iron Horde on their own soil, they would need a supply line for reinforcements. Thus, they created outposts across Draenor with magical links back to Azeroth. Unfortunately, what seemed like a prime strategic location near the Blackrock Foundry was known to the botani as The Everbloom, a sacred place within Gorgrond woodlands. The outpost was quickly overgrown, but it still contains a link to the outskirts of Stormwind...
The Everbloom instance actually contains an almost-complete instanced version of Stormwind City, devoid of NPCs, all the way to the interior of Stormwind Keep. Like regular Stormwind, it is considered Alliance territory and puts players who manage to get there into the Stormwind City zone chat.
Part of the reason that Blizzard has not fixed during Warlords of Draenor the terrain issues in Everbloom (before the first and seconds boss encounters, which allowed skip some mob packs) is the challenge mode leaderboard, fixing it would make the top times unbeatable.[1]
Gallery
Entrance
Patch changes
Patch 8.2.5 (2019-09-24): The terrain issues in Everbloom was fixed as part of the introduction of the first launch for Draenor Timewalking Dungeons. Shortcut to Witherbark was blocked by plants, which would have disappeared after boss defeat. Shortcut to Ancient Protectors was fixed, disallow players to jump over the hill while mounted.
Botani
Podling
Genesaur
Human
Infested
Gnome
Pale orc
The Everbloom
The Overlook
Alliance quests
Horde quests
Neutral quests
Botani
Draenor ancients
Genesaur (one, Yalnu)
Infested
Orchids
Mandragoras
Pale orcs
Venom spiders
[Witherbark's Branch] (H · M)
[Leafhide Penetrator] (H · M)
[Leaf of the Ancient Protectors] (H · M)
[Interloper's Mossy Skull] (H · M)
[Sol's Magestaff] (H · M)
[Spores of Alacrity] (H · M)
[Coagulated Genesaur Blood] (H · M)
[Hoof of Yalnu] (H · M)
[Desiccated Husk Shield] (H · M)
[Xeri'tac's Unhatched Egg Sac] (H · M)
[The Everbloom]
[The Everbloom Challenger]
[The Everbloom: Bronze]
[The Everbloom: Silver]
[The Everbloom: Gold]
[They Burn, Burn, Burn]
[Water Management]
[Weed Whacker]
Entrance
Patch 8.2.5 (2019-09-24): The terrain issues in Everbloom was fixed as part of the introduction of the first launch for Draenor Timewalking Dungeons. Shortcut to Witherbark was blocked by plants, which would have disappeared after boss defeat. Shortcut to Ancient Protectors was fixed, disallow players to jump over the hill while mounted. 
Patch 6.0.2 (2014-10-14): Added. 