Spark of Tyr
Sparks of Tyr are mysterious artifacts used by the titanic watcher Tyr to, in his own words, "ensure some future." They are described as being octagonal in shape and made with a strange metal, with a surface that seems to change from iron to golden depending on how they are held. The Sparks of Tyr can record events and replay them within the minds of others.
Dawn of the Aspects
During the era just after the Ordering of Azeroth, as Tyr rallied a force to battle the massive Galakrond, he held the Spark of Tyr up to five proto-dragons named Alexstrasza, Ysera, Neltharion, Malygos, and Nozdormu with the promise that he was "trying to ensure some future." During a battle with Galakrond, the Spark of Tyr was knocked free from Tyr's person and, desperate to grab it, he left himself open for Galakrond to devour his hand, swallowing both it and the Spark.
A Dalaran mage named Rulfo would later find a Spark of Tyr and receive visions of the earliest era of Azeroth. The visions eventually drove Rulfo mad, and his mangled body was found dead one day. The reports say he fell off a mountain.
Many thousands of years later, Kalecgos found the same Spark of Tyr that Galakrond devoured clutched in Tyr's severed hand at Galakrond's Rest. The Spark granted Kalec visions from Malygos's point of view of the events surrounding Galakrond and the creation of the Dragon Aspects, but risked driving him insane in doing so. Eventually, after overcoming the Spark with the help of Jaina Proudmoore, Kalec used it to show Alexstrasza, Nozdormu, and Ysera - who had become depressed following their becoming mortal with Deathwing's defeat - the moment of their first glory.
This section concerns content related to Legion.
Sparks of Tyr are needed to release the magical wards holding Tyr's hammer, , within the Tomb of Tyr beneath Tirisfal Glades. Travard sent a paladin adventurer to Dragonblight to locate Galford, who had another Spark and had gone north to learn more about Tyr. Galford was killed by Jotun, Tyr's old friend who had been cursed by Loken, but not before he had succeeded in using the Spark to see memories of Jotun aiding Tyr. After Jotun was defeated by the paladin adventurer and Lanigosa, he was briefly freed from Loken's curse and allowed the paladin to retrieve the Spark of Tyr before the curse could overtake him again.