The only fear is that the Celestial King will not dare to participate

"To the Celestial King and King Leonis:

Why should wars be fought between soldiers? Do you dare to fight king against king? This King only wishes for a life-and-death battle between the three kings, with life and death determining the outcome! If This King were to die in battle, the Infernal domain will surrender! Conversely, if you were to unfortunately die by This King's sword, please withdraw your troops! This King has penned the challenge. Do the both of you dare to fight? —The most cowardly Infernal King in all of eternity!"

The two letters with the same content were separately sent to the Celestial domain and Transcendence. It might have been done unwittingly or it might have been done deliberately, but the contents of the two letters were quickly revealed. It proliferated in the three domains, causing every commoner on the streets and the soldiers to know of the letter's content. A flurry of discussion broke out because of it.