Minecraft wiki entry for The_Wild_Update, associated text: "1) Deep Dark is the name for now, but like anything names can change. I like it though. 2) Deep Dark is one of the only Overworld biomes where only one type of enemy can spawn: Wardens. So no Zombies, Creepers, etc. 3) That is a mystery for you players to reveal in-game." – @kingbdogz on Twitter, June 17, 2021