There are multiple decentralized stablecoins out there. DAI is the most well known and works pretty well. sUSD also works well. mStable is the best of both worlds and uses both decentralized and centralized stablecoins in a basket to form an even more stable, stable coin.

They are very relevant to the discussion as stablecoins will be the primary way people interact with decentralized services and decentralized stablecoins retain the decentralized and trustless properties that make BTC and ETH valuable.