They finally added a block that damages! It also doesn't destroy items. Magma blocks. This is significantly better than having to damage things with lava, and it currently doesn't light things on fire
You can make traps for other players with it and enemies. Specifically useful for farming, although some enemies are immune to it
They added a block that is destroyed by water, which I can image to have interesting results, but not terribly useful
They added a save and load structure feature to mass copy objects in creative mode. You add 2 corner blocks and it creates an area in which you can copy ALL blocks and entities in it, then you go somewhere else and place a load block and you can load the structure. But, not only can you load the structure, it gives you the option to rotate and flip the structure as well. It only gives you the option to flip left and right though, not up and down.
The other blocks they added are more of less aesthetic, with the only difference being one is nether brick that's a different color and the other is a bone block. The bone block doesn't allow redstone signals to go through it while the nether brick does
Bone blocks can be found nature in the shape of giant skeletons underground
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As for the mobs, the polar bear is passive unless it's provoked OR has cubs. If it has cubs it becomes aggressive regardless
