The thorns does not work against some monsters such as slimes. This has been reported in MC-4609 and MC-4619 but it is still bugged (at least for me).
To verify this, I manually created a level 127 Thorns enchantment and tried it against different mobs. Zombies, Skeletons, Zombie Pigmen and Spiders instantly died. They were instantly killed on first contact, none of the them required a second time for the Thorns enchantment to work.
However, the slimes never got hurt once even though I have spawned around 64 Large Slimes and went around getting attacked by them for 5 minutes or so, with the same enchantment level.
The enchantment level 127 was obtained using a NBT file editor. A level 3 Thorns enchantment (maximum level obtainable without editors) still does not damage slimes.
Update: (Thanks to Mike B for the comprehensive coverage)
Mobs affected: Zombies, Cave Spiders, Spiders, Skeleton, Wither Skeletons, Zombie Pigmen, Endermen and Silverfish.
Not affected: Wither Boss, Enderdragon, Magma Cube, Slimes, Witch, Wild Angry Wolf, Creeper, Blaze and possibly Iron Golem. (Creeper should not be affected because they're dead after they attacked)
Video Proof: http://youtu.be/BPUWM3HvCZY
Environment
Previous Environment:
Windows 7 64-bit
Java 7 Update 9, 11, 13, 17, 21, 25, 45 (both 32-bit and 64-bit installed)
Minecraft 1.4.6, 1.4.7, 1.5.1, 1.5.2, 1.6.1, 1.6.4, 1.7.2 unmodified
Intel Core 2 Duo E6400 2.13GHz
Nvidia GeForce GT 220
Current Environment:
Windows 8 64-bit
Java 7 Update 51 (both 32-bit and 64-bit installed)
Minecraft 1.7.4 unmodified
Intel Core i5 CPU 660
Nvidia GeForce GTS 250
Linked issues
is duplicated by 2
relates to 2
Comments 14
Well, Dinnerbone said in one of his tweets that Thorns should work against everything...
https://twitter.com/Dinnerbone/status/279275058634031104
I think this must be solved. I had a level 100 Thorns on a flatworld also and it didn't affect slimes.
And I don't know if Witches should be affected by Thorns as they attack with splash potions. Maybe Witches could be affected when he uses a splash potion of instant damage, but I don't know.
For now, I'm just using Dinnerbone's tweet that the thorns work on everything. The link to his tweet was in a previous comment.
i think the blazes are having this glitch because of them having 2 types of attacks ranged and touching maybe that they arent adapted to thorns?
Is this still a concern in the latest Minecraft version 14w11b? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
Maybe intended ? Ever tried to stab a jello ?