During the WoWChakra interview with Ion Hazzikostas, the developer revealed that the runecrafter NPC that we will find within Torghast is the very same NPC who carved the runes on Frostmourne.
That NPC will join us to help us craft Legendary items from materials gathered in each Torghast run.
You can find this question at 03:05:32 in the video.
We know that one of the main rewards of Torghast is the new legendary items. Where will we craft them exactly? Is there a minimum floor that players have to reach to craft them?
Ion: This isn’t something that is available in the alpha just yet, but we hope to have it up there in a few weeks. The fantasy behind how legendaries will be obtained is that early on in your jorneys in Torghast you will recover a key that let’s you unlock a door that is near the entrance to Torghast; and in that cell, you will find this ancient runecrafter that is chained up in a room full of arcane devices.
The story is that we will come to learn that this is actually the smith who scribed the runes on Frostmourne. This is the one who crafted the Helm of Domination that the Lich King wears… or wore; and we journey through the tower, recover scraps of this ancient runic language, as well as some powerful fuel for the furnace used to forge the legendaries — this runesmith will be able to inscribe our items to turn them into legendaries with the powers of our choosing.
It should be something that will be unlocked very early on in Torghast. I’d expect players to see it probably the very first week of the expansion; but then unlocking and learning these different recipes, and obtaining the materials to craft them, will be a journey to spend in the expansion.