This article describes the details of development, design, and planned construction/deployment of the DUCK (Detector system of Unusual Cosmic ray casKades). This is a scalable cosmic-rays detector system designed to measure a variety of cosmic event properties. The primary scientific goal for the DUCK project will be an independent verification of the detection of the ‘unusual’ cosmic ray events by the Horizon-T detector system. A detailed study of events of this type upon verification is a vital step towards understanding the nature of cosmic rays, their origins, and details of interaction with the nuclei in the atmosphere. Further operations as part of other international collaborations will contribute to the continued monitoring of the other types of cosmic events.