Design Fiction has become the basic tool with which a team of European institutions has addressed the definition of use cases for the project of a future social network called HELIOS. This article aims to showcase this experience of technological conceptualization that has used a co-creation process of speculative figurations as a methodological resource. The underlying HELIOS project-funded by the EU through the H2020 program [http://heliossocial.eu]- is a proposal for a decentralized social platform. It proposes an alternative to existing networks because of its context awareness and its connectivity based on trust and transparency. Key findings of this practice-based research show a proto-toolkit on how collaborative fictional narratives are useful in innovation processes. Moreover, it presents a procedure to deal with the complexity of not-yet-existing technologies and socio-technical scenarios. The article highlights some challenges to add ethical, political, and environmental concerns to the technology development process itself.Objectius de Desenvolupament Sostenible::10 - Reducció de les DesigualtatsObjectius de Desenvolupament Sostenible::12 - Producció i Consum ResponsablesObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (author's final draft
