End Time is a heroic-only dungeon found in Caverns of Time, released in patch 4.3.0 as part of the progression to the fight against Deathwing. This first instance building up to the fight with the Worldbreaker takes adventurers into one of the many possible futures of Azeroth, revealing what will transpire if Deathwing is not stopped: the Hour of Twilight.[1]Murozond tried to ensure the End Time would come to be because he believed that this potential future where the Hour of Twilight successfully happens would still make for a much better future than the "true End Time" that he had witnessed.[2]
The Dragon Aspects that occupy Wyrmrest Temple have a problem: They know that if they cannot destroy their fallen brother Deathwing, he'll consume the world. There’s only one artifact with the power to weaken the Black Scourge, but it has long since been destroyed: the Dragon Soul. To retrieve the golden disk the Aspects must charge the heroes of Azeroth with its retrieval from the depths of time. Deathwing first unleashed the power of the Dragon Soul to stop Sargeras and the Burning Legion from entering Azeroth through the Well of Eternity. That means sending players to the Caverns of Time and Nozdormu. Upon arriving, the Aspect of Time will tell them that his ability to send them back to the battle at the Well of Eternity is being interfered with by an entity in the future. First then, players must go forward into the End Time and kill Murozond. Within they'll witness a charred vision of the world should the plan to defeat Deathwing fail.
Description from community site
One of an infinite number of potential outcomes, this timeway depicts the desolate future of Azeroth should its defenders fail to stop Deathwing. In this bleak future, Nozdormu has identified an anomaly that bars access to both the past and the Dragon Soul: a powerful creature from out of time, living alone amid time-twisted echoes of the past.
In order for Nozdormu to provide you the ability to travel back in time to a point before the Dragon Soul was hidden by Malfurion Stormrage from anyone who’d seek its power, you must first go to a distant and desolate future to discover the anomaly blocking the past. You'll find yourself in a very different Dragonblight, stripped of its snowy landscape, with little more than ruins of the once-great dragonshrines. Wyrmrest Temple itself stands only as a reminder of Deathwing's madness—what's left of his scorched remains is impaled atop the structure.
Before you confront the creature disrupting Nozdormu's access to the past, you'll first be called to fight any two of the following four ostensibly familiar leaders, chosen at random each time you play through End Time.
These long-dead heroes are mere echoes of their former glory, further warped by the corruptive force of time. Their presence here is a great mystery, even to Nozdormu. Once these shades have been laid to rest, the maniacal figure blocking Nozdormu's vision will be revealed at the End Time. None of the Dragon Aspects could have predicted what entity would have such power to interrupt the sight of the Timeless One… the ability to create a new and infinite dragonflight. Only by destroying a mysterious dragon known as Murozond will you give Azeroth's protectors the opportunity to avoid the potential outcome to which your eyes bear witness.[3]
Adventure Guide
One of an infinite number of potential outcomes, this timeway depicts the desolate future of Azeroth should Deathwing fail to be stopped. Nozdormu has identified a powerful anomaly that exists in this moment and bars access to the past - and hope of retrieving the Demon Soul. The powerful creature from out of time live alone amidst the time-twisted echoes of the past.
The dragonshrines, as well as the starting point are accessed via transportation devices. Nozdormu in his humanoid form can be found hovering near it. After defeating two of fallen heroes, the party faces off Murozond as the final boss in the Bronze Dragonshrine.
Although this timeline represents all life having been destroyed, where not even cockroaches survived, several key locations can be seen in the distance, which includes: Dalaran, New Hearthglen, and even the Surge Needle.
According to Archmage Khadgar, with the Hour of Twilight averted, the question arises whether Nozdormu's grim future has been changed or whether the victory over Deathwing was merely an expected step along the path to the true End Time.[4]
^The "End Time," I once called this place. I had not seen, by then; I did not know. You hope to... what? Stop me, here? Change the fate I worked so tirelessly to weave? You crawl unwitting, like a blind, writhing worm, towards endless madness and despair. I have witnessed the true End Time. This? This is a blessing you simply cannot comprehend. - Murozond#Quotes
Murozond
The Dragonblight.
Azure Dragonshrine.
Ruby Dragonshrine.
Obsidian Dragonshrine.
Emerald Dragonshrine.
Bronze Dragonshrine.
Echo of Baine - Obsidian Dragonshrine
Echo of Jaina - Azure Dragonshrine
Echo of Sylvanas - Ruby Dragonshrine
Echo of Tyrande - Emerald Dragonshrine
Black dragonspawn
Black drakes
Bronze whelp (one, Alurmi)
Bronze wyrm (one, Nozdormu)
Cockroaches (critters)
Dwarves
High elves
Humans
Infinite dragonspawn
Infinite wyrm (one, Murozond)
Geists
Ghouls
Plague eruptors
Sabers
[35D] The End Time
[35D] Archival Purposes
The Ruby Dragonshrine
The Bronze Dragonshrine
A Time Transit Device
Hotfix (2015-11-20): Players are now scaled to item level 350 (up from 300) while Timewalking in End Time. 
Patch 4.3.0 (2011-11-29): Added. 
Icy Veins End Time walkthrough
