Gwess, a Green Dolphin Street Prison inmate serving twelve years for arson, attempted murder, and parole violation, first encounters protagonist Jolyne Cujoh as her cellmate. Masking her volatile nature behind a veneer of camaraderie, Gwess feigns generosity—offering food and returning a stolen pendant—only to weaponize her Stand, Goo Goo Dolls, which shrinks victims to rodent proportions. Those ensnared by her power become unwilling “pets,” confined within hollow animal skins and coerced into mimicking infantile speech.

Her interactions with Jolyne oscillate between calculated charm and explosive aggression. When defied, Gwess retaliates with psychological torment—shattering possessions, threatening lethal force, and exploiting her Stand to coerce Jolyne into perilous escape-related tasks. This manipulation halts when Jolyne’s awakened Stand, Stone Free, overpowers her, reducing Gwess to a grudging subordinate.

Post-defeat, Gwess offers tactical counsel on prison survival, advocating ruthless enforcement of social debts to command fear. Though Jolyne dismisses her as duplicitous, Gwess’s insights occasionally prove shrewd. Her bravado crumbles during the Jail House Lock incident, exposing latent cowardice when stripped of dominance.

Goo Goo Dolls’ shrinking effect wanes as distance from its target increases, a vulnerability Jolyne exploits to reverse her diminishment. Gwess acquired her Stand through a pendant obtained from Ermes Costello, secretly imbued with a fragment of a Stand-granting Arrow. Her pragmatic streaks surface in her grasp of prison hierarchies, yet self-interest consistently governs her actions.

Visually defined by three dots beneath each eye, avian-themed accessories, and a striped uniform, Gwess operates as an opportunistic transient ally. Her narrative relevance wanes after pivotal arcs, but her blend of cunning, cruelty, and frailty underscores the carceral setting’s themes of power dynamics and psychological exploitation.