Hi. When I created a world in pre-release 3 of Minecraft 1.16 for seeing the new Nether Fortress spawn rate, I went to some of them and all of them were infested of wither skelletons. There were always a minimum of 3 wither skelletons atacking me, and when I killed one another appeared. They spawn with a lot of frequency.
How to replicate:
Create a new world
Go to the nether
Locate a Nether Fortress
Fly around on creative or explore it in survival, you'll see a lot of our tall black-boned friend.
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However, we are already tracking this issue, and this report is a Duplicate of MC-182170, which is a report that has not been resolved yet.
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