Arcane Sanctuary (quest)
I've been researching the old records, trying to find the location of Tal Rasha's Tomb. Though I haven't found the Tomb, itself, I may have a good lead for you.
The great Vizjerei Summoner, Horazon, built his Arcane Sanctuary somewhere around here. He was a powerful spellcaster and kept demons as slaves within the Sanctuary. He kept a close eye on great events, too -- such as the imprisonment of Baal within Tal Rasha's Tomb.
If you could find Horazon's Sanctuary, I'm sure that it would hold some clue as to the Tomb's location. Though I doubt Horazon is still alive, you must proceed with caution. There's no telling what could be waiting inside.
When I spoke of this with Lord Jerhyn, he asked that I send you to him. Perhaps he knows of a secret entrance or the like. - Drognan
When the troubles began here, I allowed the terrified Harem guilds to join me within the safety of the palace. All was fine, until one night...
Screams echoed up the stairwells from the harem. My guards arrived to find the poor girls being slaughtered by a merciless band of hell-spawned demons. My brave guardsmen tried to push the demons back into the mysterious rift from which they came.
Ever since, my men have fought a losing battle. Demons have continued to pour through the rift into the palace. Ultimately, I hired Greiz and his mercenaries to help protect the rest of my fair city.
Drognan believes that the Arcane Sanctuary lies buried underneath this palace, since Lut Gholein occupies the site of an ancient Vizjerei fortress.
My palace is open to you now... Take care. - Jerhyn
The missing Seventh Sign marks the Tomb of Tal Rasha... Of the Horadrim he might be called the foremost.
It was a shining - but brief - moment for the Mage Clans when they set aside their differences and worked together against the common enemy.
The Horadrim relentlessly pursued the Three across the desolate Empires of the East, and even into the uncharted lands of the West, leaving the Archangel Tyrael's hands unblemished.
Presuming the Three to be vanquished, the Horadrim's unstable fellowship began to dissipate. Abandoning their sacred charge to safeguard the three Soulstones, the disparate Mage Clans began to squabble amongst each other over petty differences.
Their conflicts not only dissolved their brotherhood, but strengthened the Evils which they had buried beneath the cold earth. - Horazon's Journal