The film's exploration of identity and selfhood is a central concern, particularly in the character of Lena (Natalie Portman). As Lena navigates the Shimmer, she confronts the possibility of her own annihilation, both physically and ontologically. The Shimmer's strange, hybrid creatures and landscapes serve as a mirror to Lena's own psyche, reflecting back her own fragmented and dissolving sense of self. The film suggests that the self is not a fixed, essential entity but rather a fluid, dynamic process that is always already implicated in the natural world.