Betraying Devlin was done by Emperor Charlotte Grey.
If you hate someone, you must make sure they die.
But Devlin is from the Undead Tribe.
Wanting to die is very difficult.
Perhaps, sometimes living is the real torment.
Emperor Charlotte Grey teamed up with Kyler Reed to lock Devlin in the lightless Black Prison.
Later, they even sought out the Funeral Alliance, spending a large sum to buy a dagger, planning to send someone into the Black Prison for assassination.
Unexpectedly, Mr. Ghost from the Mountain of Leaving was released inside the Black Prison, causing the Black Prison's pride, the steel prison, to be breached!
And Devlin actually walked out of there by sheer luck and even boarded Sutton's ship, safely leaving the Black Pine League.
Miscalculation.
Emperor Charlotte Grey knew Devlin wasn't dead and indeed felt somewhat disappointed.
But he also understood that this matter must not be leaked.
