We present a comprehensive description of Hydra, the largest darknet marketplace in the world, until its shutdown in April 2022. We document the main features of Hydra, such as dead-drop delivery, feedback and reputation system, escrow, and dispute resolution. Using data scraped from the platform, we quantitatively examine the marketplace’s scale and structure. We find that it had been highly competitive and also allowed the wholesale trade of drugs and precursors. The dead-drop delivery system used on Hydra was expensive, as the courier costs comprised a substantial proportion of the sale price of drugs on Hydra. We contribute to drug cryptomarket research by studying an unprecedentedly large non-Western marketplace that existed substantially longer than any other known darknet market. The phenomenon of Hydra shows that shutdown policies applied to darknet marketplaces have a substantial effect and implicitly shape the whole drug market. Without these policies, a pervasive digitalization of the drug trade can occur. The primary cost of allowing marketplaces to grow is the probable increase in the consumption of illegal drugs due to convenience for consumers and facilitated cooperation between suppliers. This cost must be weighed against the potential benefits, including a higher quality of drugs, decreased potential violence, and the incentives for a large marketplace to self-regulate. The case of Hydra also suggests the relevance of financial regulation to limit the growth of darknet marketplaces.