People used their souls to power the ancient energy source, however it ended up being used to destroy them via corruption, and this is why Imu referd to it as one of 3 things needed for domination.
Oda has been building up and setting up Usopp for this for over 20+ years. Even during Elbaph Oda has given Usopp so much set up and growth. Usopp currently has the "Brave Warrior" mindset and is ready to save Elbaph.
"I thought this was supposed to be Usopp's arc"
Yall make jokes but from his point of view the thing that was supposed to be the greatest moment of his life turned into hell
"I thought this was supposed to be Usopp's arc"
Yall make jokes but from his point of view the thing that was supposed to be the greatest moment of his life turned into hell