Minecraft's Caves And Cliffs update was so big it got split into two, but even still there were other ideas that got pushed further back. Some of those ideas will feature in the The Wild Update, which now seems to be edging closer to its own release. Yesterday, Mojang launched the first 1.19 pre-release update - and showed off some of its new creatures in a developer livestream.
The Wild Update will liven up Minecraft's world with new biomes, Mangrove Swamp and the Deep Dark, as well as new mobs to populate them. One of those mobs is the Warden, an antlered, inky, sad-faced behemoth from the Deep Dark. The Deep Dark and the Warden were both intended features of the Caves And Cliffs update before being pushed back to 1.19.
You can see the process behind creating the Warden in yesterday's livestream:
That video also offers insight into other parts of the update, including the frogs that live in the revamped swamp biome, the Mangrove Swamp. The frogs are considerably cuter than the Warden.
If you're not familiar with Minecraft's update process: Mojang release "snapshot" updates on Wednesdays for the Java Edition in order to roadtest new features, then shift to "pre-release" updates that consolidate those snapshots and focus on bug fixes. The pre-releases don't add a lot of new content, but the shift towards polishing and bugfixing marks a significant step towards the full release of any update.
You can read about what is included in v1.19 pre-release 1 on the Minecraft site. It mostly contains bug fixes, but there are some interesting balance changes too, including increasing the number of Endermen and other creatures that spawn in the Nether.
As noted above, snapshots and pre-releases are only available for Minecraft: Java Edition. If you want to explore the new biomes without waiting for the full release, you'll need to enable snapshots within the "Installations" tab of the Minecraft launcher.