"Black Gilgamesh," also known as "Shadow Gilgamesh," physically embodies the accumulated vices, sins, and inner darkness of the original King Gilgamesh. This entity emerged from Gilgamesh’s prolonged tyranny and corruption after he gained immortality and ruled Babylim. Though immortality initially blessed him, the burdens of kingship—coupled with the trauma of his son’s death and his wife’s decline—fractured his psyche and eroded his soul.

Following Gilgamesh’s defeat of Druaga, his endless lifespan and unchecked power twisted him into a despot. This moral decay allowed his negative traits—arrogance, cruelty, and disdain for humanity—to coalesce into a sentient entity. Shadow Gilgamesh acts as Gilgamesh’s "enemy within," embodying the king’s suppressed malevolence and hunger for absolute dominion.

In the anime’s second season, Shadow Gilgamesh serves as a primary antagonist. He manipulates events from within the tower, exploiting characters like Neeba by promising power and validating their resentments. His influence drives Neeba to betray allies and pursue destructive goals, culminating in Neeba’s transformation into a new incarnation of Druaga. Shadow Gilgamesh’s ultimate aim is to perpetuate chaos and secure his dominance by corrupting tower ascenders.

His existence is intrinsically tied to Gilgamesh’s immortality: since the king cannot die naturally, Shadow Gilgamesh cannot be eradicated conventionally. This dynamic traps Gilgamesh in perpetual internal conflict, forcing him to confront the entity as an inescapable aspect of his own corrupted legacy. Shadow Gilgamesh’s presence underscores the consequences of Gilgamesh’s fall from heroism to morally compromised rule.