Endometriosis affects 1 in 10 women and many gender-diverse individuals, causing chronic pain, digestive issues and mental health impacts like anxiety and depression. Despite its prevalence, it remains underdiagnosed and misunderstood. This thesis explores how design can express the lived experience of endometriosis through speculative and participatory methods. Through research and co-creation with patients and doctors, a reflective card deck was developed. The cards embody visual representations of the condition – its appearance, characteristics, limitations and capacities alongside blank cards for self-reflection. The deck serves two purposes: internally, to support self-understanding among those with the condition; and externally, to raise awareness and improve patient-doctor interactions. This project shows how speculative design can give form to invisible struggles and bridge gaps between clinical understanding and personal realities.