The main focus of 0.9.0 was two new features. The new temperature system along with the new Quivers system. There's also a few quality-of-life changes and fixes in this patch too.
Changelog---------------
0.8.3 --> 0.9.0
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# ADDITIONS
- New temperature system:
- The maximum temperature is now 100 and the minimum is 0.
- You can now only lose temperature at night or during rain/snow.
- You can now gain temperature by standing near a fire.
- You can no longer die of low/high temperature, instead you will black out at 0.
- Low temperature will now continuously effect stats (energy, hunger and sanity).
- Added a quiver (bear/rabbit fur + leather). Can be equipped as normal.
- Equipping the quiver will allow you to store a maximum of 20 arrows.
- Double-clicking arrows will now add them to your quiver.
# CHANGES
- The "Faded GUI" option now also applies to the blood content bar.
- Increased the speed at which arrows move.
- The charge bar will now instantly appear after holding down RMB.
- The "Faded GUI" option will now be off by default.
- Music and sound options will now go up/down in intervals of 5.
# FIXES
- Fixed swimming in non-existant water.
- Fixed an error with the merchant spawning in multiplayer.
Major highlights
The new temperature system, as listed above, is designed to be more intuitive. The previous one had a lot of stages and a lot of consequences for low/high temperature - this one only has a few. Read the changelog above for all the new changes to the temperature system.

The Quiver system is a new way to organise your arrows. Previously, each arrow would take up one inventory space but with this new system, each quiver can hold a maximum of 20 arrows (you can only have one quiver equipped at any one time). If you have a quiver equipped, the arrows will automatically go into your quiver (if you have space).