Justice Light's undisclosed plan for the recovered gate artifact, which Carl judges to be revenge.
Justice Light insists that getting the gate back will make everything else irrelevant, and demands that Carl tell him where it is and send the Sluggalos back to him. Tipid refuses to help precisely because Justice won't say what he needs it for, and both he and Rosetta are hesitant and overwhelmingly protective of the eccentric skyfowl.
Carl doesn't understand what Justice is doing with this "antenna" either, and reasons that the reason he won't say is that it's dangerous, or stupid, or probably both. Remembering Rosetta beheading King Rust and sobbing with centuries of relief afterward, he decides he is not the man to stand between a brother and his revenge — because clearly that is what this is — and names Paca in the Midnight Market.
The skyfowl's secret purpose for the artifact, unnamed but recognized by Carl as vengeance.