|This page contains spoilers for:||Pantheon (short story)|
In the Age of Myth, Sanasay dwelt with his wife and children in the city of Andamar in the Realm of Ghyran and there was acclaimed as the finest thinker in the realm as well as the powerful mage. However despite his renown; happy family life and unmatched powers he grew restless, wanting a challenge and to find his true purpose in life. He sought the advice of the god, Teclis the Wise who impressed with his skills, set him on the path to find his way to Realm's End, a place of purest magic where he could gain untold knowledge and eternal life, but he also warned him that his quest may not bring him the satisfaction he sought.
He travelled to the Iron Temples to Grungni in the Realm of Chamon’s Ferron Vale and to the gates of where he sought where he was confronted by Afrener the guardian of the gate, the wolf at the door - a massive beast that only Death could kill. He finally was forced to plead a favour from Nagash himself who granted his wish in exchange for 500 years’ service upon his inevitable death. Finally he reached the object of his quest and found a daemon of Tzeentch waiting, although he did not at first recognise such a mythical creature.
Following a confrontation with that entity he returned home to his family but also warned the Pantheon that Chaos was now encroaching on the Mortal Realms and he created a potent magical artefact, the Mirror of Bayla for them to scry any location in the realms. 
He was an extremely powerful mage - enough that Nagash was willing to grant him a favour in order to gain his services in the future and that Sigmar said he could have joined the ranks of the divine. Confronted by a powerful daemon of Tzeentch, he was able to easily destroy it - casting its essence to the maelstrom. 
He wrote On Realm's End about his experiences. 
|I have unlocked many of the mysteries of the world. I have mastered five of the eight schools of pure magic. I understand the rest well enough, and know sufficient of the darker arts to leave them alone. Every question I ask, I find the answer to. I am bored, my wife. I must set myself a challenge that will test me. I need a purpose. I need to know why I do what I do, and to what end I should put my great knowledge
~ Sansay to his wife.