Why did Darius plant the Soul Curse here? Well, the reason was quite simple. The true level of power and the true difficulty would present itself starting from the Adept hives.
After he planted the Soul Curse here, it would take some time to spread competently as different hives would infect each other over time. However, as time was the most precious thing now, Darius would have to use shortcuts to achieve his goals within the time limit.
Namely, by poisoning the Adepts here.
Once he rose back up, he would begin the slaughter from where Gunner and co had left off, some Insects that they would intentionally allow to survive would then proceed to send news down about the culling.
This would make it so that those down below would start to panic due to the power of the three, and they would also send out messengers further down.
