The Axolotl is a cute new mob in the 1.17 update. It spawns in underground lakes and can be tamed with tropical fish. In the category Axolotl% you have to get tha advancement: The healing power of friendship. You get the advancement when you win a fight with an Axolotl.

It would be nice, if a new category would be edit, where you need to get one piece of iron armor.