Board Thread:Lore Discussion/@comment-11215761-20130729041940/@comment-89.245.234.144-20130819184223

@Sky Above, Voice Within

Yagrum was in the "Outer Realms" and because the Heart of Lorkhan is connected with Mundus, only the Dwemer on Nirn were affected by that what Kagrenac did. Some other people say, that Yagrum was intentionally left over, because he was maybe the one who was supposed to activate Numidium.

@Dovahsebrom

The Heart of Lorkhan isn't exactly a soul gem, it's the thing that contains Lorkhan's power. Also, the warped soul gem is, as Entir (or what was his name?) says totally useless because it can't catch a soul. I think that Arniel did what Kagrenac did, but on a much smaller scale. It's possible that the souls of the Dwemer became the Brass Skin of Numidium, or in other words, they bound themselves to the nearest divine being(which was Numidium). Arniel did that too, but the nearest divine being was in his case the Last Dragonborn.