On latest preview, the Creaking dies in 1 hit from most things.
You can kill him in survival!
He dies from falling!
Even lava kills him!
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I believe that it is work as intended, only creaking that summoned by Creaking Heart can not hurt by everything
Thank you for your report!
However, this issue is Working as Intended.
The report you have submitted is working as intended: see the 1.21.50.20 Preview changelog.
The Creaking Spawn Egg will spawn a Creaking mob that is not connected to a Creaking Heart. The Creaking mob will persist through day and night, loads and saves, and will take damage from attacks and other damage sources. It has one point of health (half a heart).
Please note, that mechanics of the game may change between updates.
Things such as graphics, sounds, world creation, biomes, redstone, villagers, and animals may not work the same in current versions.
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