Seeds of their Demise is a talent for Hellcaller Hero Talent for Warlocks, it’s tooltip states with the tooltip linked above.
The issue is, during the Beta the effect of this was quite different, offering a damage increase of 30% to Blackened Soul.
The issue is that, once reworked while the new effect got introduced and the tooltip changed, this +30% damage to Blackened Soul either stayed or got re-introduced due to itteration divergence on its effects listed as effect nº3.
As Such, this talent, beyond doing what it actually does, it also offers an damage increase of 30% to blackened Soul.
Blackened Soul is a significant damage portion of Hellcaller Destruction and a smaller but still valuable portion of Hellcaller Affliction.
How to test:
A - Check the damage value of Blackened Soul utilizing its %spellpower + damage modifiers
B - Check Damage done of Blackened Soul on Combat Log
C - Compare them and notice Blackened Soul deals 30% more damage.