I'm aware that it is possible to change loot tables for mobs in Minecraft 1.9, making Ender Dragons drop an Elytra for example. This can be done either by creating a custom loot table or changing its entity data. For this example the command would be the following:

/entitydata @e[type=EnderDragon,tag=!hasTable] {ArmorDropChances:[0:1.1f,1:1.1f,2:1.1f,­3:1.1f],ArmorItems:[0:{},1:{},2:{id:elyt­ra,Count:1},3:{}],Tags:["hasTable"]}

Considering this, how would it be possible to make it so that Wither Skeletons always drop a skull?

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1 Answer

I can't do it with loot tables, but I can still help you. Get a repeating command block and input:

/scoreboard objectives add test stat.killEntity.WitherSkeleton

Next, in the same direction as that command block is facing, place a chain command block and input this:

execute @p[score_test_min=1] ~ ~ ~ summon minecraft:wither_skull ~ ~ ~

which is good if your inventory is filling up fast, or

give @p[score_test_min=1] minecraft:skull 1 1

which is great if you're on a server and don't want people pinching your skulls. Next place another chain command block with:

/scoreboard players set @p[score_test_min=1] test 0

Note: Replace 'test' with the name of a scoreboard of your choosing, set the repeating command block to always active and unconditional, set the others to always active and conditional. This is multiplayer-friendly.

Bonus: If you use this for something more common (like cows and leather, for example), you might want to limit the availability by imposing a second requirement. To do this, put another repeating command block in place. Whichever repeating command block is closest to the chain command blocks can be a chain command block, but it must be set to conditional.

An example of a different kind of restriction is:

{SelectedItem:{id:minecraft:iron_axe,tag:{display:{Name:"Sacrificial Axe"}}}}

Best of luck!

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