Titanic Watchers/Keepers

In addition to the Titans are the Titanic Watchers. While these creatures resemble Titans, they're something else entirely. Created by the Titans (presumably in their own image), the watchers were charged with watching the creations of the Titans and making sure everything was working correctly. Much like the Dragon Aspects, the Titanic Watchers and Keepers were essentially fail-safes to guarantee the Old Gods didn't take over again and that life on Azeroth would continue in an orderly fashion. Most Watchers and Keepers are found in Northrend, though others have been discovered here and there:

• Ironaya: Ironaya is located in Uldaman, a titanic stronghold located in the Badlands. Ironaya seems to have been charged with watching over and protecting the secrets contained within Uldaman's vaults, and players have to kill her to advance into the vaults. It's not because she's evil, insane, or otherwise corrupt -- she's simply doing her job and trying to keep the secrets of the titans safe.
• Myzrael: Myzrael is a "princess of the earth" and has been imprisoned in the Arathi Highlands. Why? Well unfortunately the Old Gods managed to drive her completely insane, and the mountain giants that were created to protect the world discovered her madness. Much like the creatures that created them, the mountain giants decided that the best way to deal with something involving the Old Gods was to stuff it under the earth where it couldn't hurt anyone. The Twilight's Hammer has been trying to free her in order to use her for whatever horrible plans they've got brewing -- knowing the Twilight's Hammer, you can bet the Old Gods are involved.
• Maiden of Virtue: The Maiden of Virtue is present in Karazhan, of all places. What she was originally created to watch over is unknown, and how she arrived in Karazhan is also unknown. It's entirely possibly that Medivh placed her there some time during his residency in the tower, considering the Guardian enjoyed collecting all sorts of oddities.
• Stone Watchers: Stone watchers are other minor watchers put in place for varying reasons, usually to guard access to certain things. These guys are sprinkled all over Azeroth, either to guard access to information, to guard relics, or to guard ... well, just about anything. They guard. A few notable stone watchers are as follows:
  • Archaedas: Archaedas has also been charged with watching over Uldaman, specifically the vault of the stronghold. Players also have to kill Archaedas when running through Uldaman -- but much like Ironaya, he is neither insane nor corrupt -- he's simply carrying on with the job he was assigned to do.
  • Lore Keeper of Norgannon: The Lorekeeper exists in a few different areas -- from what we can gather of the name, it looks like Norgannon placed these stone watchers in various areas to safeguard vital information about the development of Azeroth.

As for the Titanic Watchers and Keepers of Northrend:

• Thorim: Thorim was the guardian of Ulduar, a titan stronghold that was part research facility, part prison of the Old God Yogg Saron. Thorim didn't live in Ulduar proper, his home was the nearby Temple of Storms -- however, he mostly patrolled the areas outside Ulduar, protecting the facility and forging alliances with the frost giants in the area. This would have been still functioning exactly as planned were it not for ...
• Loken: Thorim's brother Loken was the "supreme protector" of Azeroth, otherwise known as the "prime designate" of the Watchers of Ulduar. Unfortunately it seems as though Loken watched over Yogg-Saron's prison a little too closely, and he fell under the sway of the Old God. Loken apparently learned the lessons of chaos quite well from Yogg-Saron, as most of his activities after that point were done specifically to sow chaos and discord through the ranks of the Watchers. He killed Thorim's wife, Sif, and framed the ice giants for it. He systematically took the other Watchers down one by one, and each joined him in Ulduar, where they fought to defend the stronghold against any who would seek to destroy the Old God.

Loken wasn't just the "prime designate," however. Players are asked to seek out and kill him in the Halls of Lightning -- and those that continue into Ulduar discover just how bad that idea was. As the prime designate, his destruction was considered the first warning sign that the planet of Azeroth had failed -- that the Old Gods had somehow managed to take over. In the event of his death, the Titans would be signaled -- and this time, they wouldn't try to simply lock the Old Gods away. When they returned, they would do what they had to, destroy the entirety of Azeroth and all living creatures upon it, and start over from scratch. When players killed Loken, his death sent off a signal to the Titans, who then sent Algalon, a creature that was simply called "the Observer," to check in and see if everything was running smoothly. If the answer was yes, everything was okay, he would send a signal back telling the Titans that all was well -- if the answer was no, then he'd send off the signal calling for Azeroth's destruction.

Basically, by running through and completing the Halls of Lightning, players were pretty much setting up the destruction of Azeroth. It made for a very interesting hard-mode encounter in which it was made clear that the world would be destroyed if Algalon was not stopped from sending that signal.

• Hodir: Hodir was also a Watcher of Ulduar. His particular specialty was the frost giants of the region -- the frost giants even believe him to be their creator, though that assumption is false. Hodir disappeared after Loken's betrayal, and it was revealed that he fell under the sway of the Old God in Ulduar.
• Mimiron/Mimir: Mimir was another of Ulduar's Watchers -- he stayed primarily in the Temple of Invention until Loken's betrayal, at which point he joined the other corrupted Watchers in Ulduar. While it is unproven, the general appearance of Mimir, or Mimiron, suggests that he was the original inventor of the mechagnomes, who eventually evolved into the gnomes we know today.
• Freya: Freya was yet another of Ulduar's watchers, and much like her creator, Eonar, she watched over all things living. The Scourge of Northrend was a source of concern, and she left an Avatar of herself in Sholazar Basin to protect it from the Scourge. After Loken's betrayal, she too fell under the Old God's sway within Ulduar.

• Maiden of Grief: This Titanic Watcher sits in the Halls of Stone. Her purpose is unknown; though her name suggests she was somehow related to whatever purpose the Maiden of Virtue was intended for. Unfortunately we can only speculate on the purposes of the Maidens -- I like to think that the Maidens, being named after emotions rather than objects, were placed to safeguard the mortal races, to watch and make sure that no matter how strong the emotions of those mortal races ran, logic and order would prevail over irrational emotion and chaos. It's only a theory, however.
• Tyr: The Watcher Tyr is as much of a mystery as his whereabouts. He once lived in the Temple of Order, and the name suggests that he was there to watch over the world and make sure that order and justice prevailed. We were given a small piece of his backstory in a chat on the official forums with the Creative Development team:

Bornakk

Long ago, on the continent that would eventually become known as the Eastern Kingdoms, a small group of creatures struggled to survive, using the limited supplies provided to it by parents who had just abandoned their children on an unfamiliar shoreline. These creatures, eventually called "humans," would occasionally take to gathering around a fire whilst trying to read from scrolls telling of ancient heroes and leaders – tales from the civilization that had cast these creatures out. One of these scrolls spoke of a great leader, a paragon of order and justice, who sacrificed his right hand in a fight against an unfathomable evil. Although it was within this hero's power to fix his hand after the fighting had ended, the hero instead chose to replace it with a closed fist made of the purest silver. In this way, the hero impressed upon those who followed him that true order and justice can only be accomplished through personal sacrifice. This hero, who slipped into memory long ago, went by the name of Tyr.

source

And as for Tyr's current location, the devs only had this to say:

Bornakk

The watcher Tyr was not in Ulduar when adventurers finally freed the titan city from Yogg-Saron's influence. If anyone knows where Tyr is now, he or she isn't speaking up.

source

• Jotun: The last of the Titanic Watchers of Northrend is Jotun the Curse Bearer. This Watcher's purpose is a complete mystery. Out in Dragonblight, he can be found endlessly patrolling the broken Path of the Titans. His name may possibly be a reference to the Curse of Flesh that the Old Gods originally put upon the creatures of Azeroth, but it's unconfirmed at this time.

As for the Pantheon and its current location? Nobody knows -- it's presumed they are out there somewhere in the universe, creating and organizing more worlds and fighting the Burning Legion. Will we ever see the Titans? Maybe someday -- until then, we can only speculate and marvel at the sheer power this group of Eternals holds. After all, they were responsible for not only the dragonflights that watch over us, but also Azeroth itself. It's a safe bet to say we haven't seen all of the Titanic Watchers that Azeroth has to offer, or the Pantheon of Titans themselves -- with the introduction of Uldum in Cataclysm, we should be getting more information on these elusive Eternals and the order they so carefully cultivate.