Dark pools have long powered institutional trading from the shadows, allowing investors to move billions without jolting markets. Today, they handle a large share of equity volume, praised for reducing costs and slippage but criticised for eroding transparency. Now the concept is leaping into crypto where stablecoins and tokenised assets fuel experiments with decentralised dark pools. Advocates say they could bring efficiency, privacy and stability whilst critics warn of deepened inequality and weakened price discovery. The real question is whether these hidden venues will evolve into a fairer global liquidity engine or remain tools for the market’s elite.