Background

Death messages are now translatable.

The bug

However, the death.attack.magic.player death message is untranslated.

Causes

This is most likely caused by the translation string not existing in the en_us.json file itself.

How to reproduce

1. Either find or spawn a Zombie with this command:

   /summon zombie
   

2. Get close to the Zombie and then let it deal damage to you. When done, run this command quickly:

   /effect give @s instant_damage 1 5 true
   

   → As expected in the first picture, you will notice that it displays death.attack.magic.player instead.

Possible fixes

This can be fixed by using a resource pack which can be downloaded below; or if you want to create your own, just follow the steps for creating one. Your en_us.json file must be on the assets/minecraft/lang folder of your resource pack and should have this code:

{
  "death.attack.magic.player": "%1$s was killed by magic whilst trying to escape %2$s"
}

As expected in the second picture, it is fixed with the resource pack we have just created. However, this should be fixed for other players by modifying the en_us.json file on the .jar itself in order to include the translation string.