If you specifically want the new 1.21 features (Trial Chambers, the Mace, the Breeze), you cannot use Eaglercraft. You must use the official game.
Eaglercraft 1.21 attempts to bring the update (Mace, Breeze, Heavy Core) into your web browser. Since true 1.21 game logic (like wind charges) is incredibly hard to emulate in JavaScript, this version is primarily a visual and item overhaul of the standard Eaglercraft base. eaglercraft 1.21 1
: A new hostile mob that jumps and fires wind charges, similar to a Blaze but wind-based. If you specifically want the new 1
If you want a "modern" Eaglercraft experience, here is the current reality: Since true 1
You should only access or download Eaglercraft files from reputable community repositories. Never input your official Microsoft/Minecraft account credentials or financial information into an unofficial Eaglercraft site. a local offline version of Eaglercraft? Nate2018/Eaglercraft-1.21.1-TeaVM - GitHub