Julian Solo acts as the mortal host for Poseidon, Greek god of the seas, and inherits the affluent Graad Foundation. Poseidon's spirit awakens within Julian during the deity's scheme to flood Earth, leading marine forces from an underwater temple. Athena confronts Poseidon there, where Julian offers her a choice to contain the deluge within the Oceans' Central Pillar to lessen the disaster. While Bronze Saints battle Poseidon's marine commanders, Gemini Kanon emerges as the hidden architect behind the god's resurgence. Confronted by the Saints, Julian becomes fully overtaken by Poseidon's divine will, overpowering them. Freed by the Saints, Athena seals Poseidon's spirit inside her amphora, halting the immediate danger. Later, in Elysion, Poseidon briefly reawakens through Julian to assist the Saints against Hades. Acknowledging Hades' threat to all realms—including the oceans—Poseidon lends his divine power. This aid enables the Bronze Saints to attain the God Cloths needed to confront Hades, underscoring Poseidon's commitment to cosmic equilibrium despite prior conflict.