What changes underground?

Environment and combat details from the reveal
FeatureAnnounced detailHow to read it
Ice caves Underground biome with ice and calcite An exploration environment, not the new dimension
Icicles Form on the ceiling A building detail; falling damage should not be assumed
Ice crystals Grow on the ground and give off soft light A decorative option; no numeric light level is given
Frozen zombie variant Hits cause freezing; some throw ice balls Distinguish melee contact from ranged attacks

Source · www.minecraft.netMinecraft Live recap

Ice cave with hanging icicles, floor crystals, distant mobs and lava on the right
Announced ice cave, shown during development · Image: Mojang Studios / Microsoft
Source / rights
Image / usage information: © Mojang AB / Microsoft. Official Minecraft editorial media; source attributed, no ownership or endorsement claimed. · Image source ↗

Should you change versions to look for them?

Check the feature list for the exact build you plan to install first. Read the build notes before searching for a newly announced feature. The broadcast alone does not tell you which installation contains it.

The reveal leaves the mob’s final name, spawning rules, drops and damage values unspecified. Wait for those details before committing to a farm design or location guide.

Where does the new dimension fit?

The Sift has its own announcement and game context. Follow the dimension article below for that distinction, or the Snapshot 2 article for a test build you can install.

Related guides

Minecraft The Sift: New dimension and Dungeons II differences

Minecraft 26.4 Snapshot 2: Changes and a separate test world