There is a lot of activity when it comes to Proof-of-Stake (PoS) cryptocurrencies, where the most popular options include Cardano (ADA/USD), Ethereum (ETH/USD), and Algorand (ALGO/USD). Vitalik Buterin, the co-founder of Ethereum, added a new category of milestones to the technical roadmap and introduced the Scourge in an expanded six-partechnical roadmap.