I don't think the Soul Weapon (SW) automatically passes on to the new heir. If it did, then Seira would have already known that her father had died before Gejutel came to tell her. I think there must be some sort of ritual or ceremony where the SW is "bestowed" upon the heir.
I think that under normal circumstances the heir is chosen by the Clan Leader before they go to eternal sleep and the SW may be passed on at the time that the Clan Leader goes to sleep.
There must be some other way to transfer the SW when the Clan Leader dies another way. Seira didn't receive the SW automatically, Gejutel told her that she would have to accept the title of Clan Leader since she was the only heir. (I wish the authors would show a flashback of her receiving the SW)
If the SW needs to be summoned by the Lord to be transferred, then the heirs of the traitors would not be able to inherit the SW.
Then there is the question of how Rael received Grandia. I think his father gave it to him before he went to eternal sleep and Rajak received his part afterward. (speculation)
There must be some other way to transfer the SW, but I can't think of what it could be. (sighs in frustration)
Edited by SevenSeven, 07 November 2013 - 11:49 PM.