I built two types of mob traps. One MFR based: mob spawners(from vanilla minecraft) + grinder.

enter image description here

As you can see there is tesseract which transfers mob drops and MobEssence to Auto-Enachnter (MFR) and Auto-Anvil (MFR) which do the work.

The second one is OpenBlocks/ThermalExpansion based. Couple of Autonomous Activators filled with swords (possibly made of Tungstensteel which have durability about 5000 and enchanted on durability and looting) which will attack nearby mobs, and a Vacuum Hopper (OpenBlocks) to suck dropped items and, the most important - experience orbs. After - transfer it to Auto Enchantment Table (OpenBlocks):

enter image description here Something like this. I use this trap to kill mobs one by one by teleporting them using portal gun. So the question is - is there common sense to build such complex (comparatively to the first one) mob trap to get liquid XP instead of Mob Essence? I can see that Auto Enchantment table from OpenBlocks works much faster (instantly), does not require energy and liquid XP is more bright (which is just good looking) and has more uses - it can be absorbed using xp shower or tank (OpenBlocks). But HUGE disadvantage of Auto Enchantment table from OpenBlocks is that it doesn't enchant books.

So how can I calculate real cost of liquid xp and mob essence? Other words - how can I calculate how many zombies should I kill by each trap to get 30 lvls cost enchantment?

  • Sorry if this is a dumb question, but how do the autonomous activators count as player kills and drop XP?
    – Atutouato
    Commented Apr 30, 2014 at 22:58
  • @Atutouato, well, experience orb, according to wiki, is an entity similar to an item entity and are dropped when a killed mob's corpse vanishes. It doesn't matter how mob died - fell from a high place, burned, was killed by a player or just choked. When mob's corpse vanishes experience orb appears. I often found a lot of them in mined quarry... I was always curious why do mobs die there...
    – Dmytro
    Commented Apr 30, 2014 at 23:32
  • Are you using Feed The Beast for your mods? If so, I would tag your question as such.
    – MBraedley
    Commented May 1, 2014 at 11:22
  • @MBraedley, no, it's not Feed The Beast.
    – Dmytro
    Commented May 1, 2014 at 14:51
  • @DmytroTsiniavskyi, I quote from the wiki: "In general, mobs drop experience orbs if they were killed by the player, but some of the damage can be done by other means. Specifically, a mob will drop orbs if it was hit by a player or tamed wolf, within the last 3 seconds (60 ticks) before its death". Your automated mob system should have no experience orbs. Are you using that machine from Liquid XP that allows any nearby mob kills to count as player kills?
    – Atutouato
    Commented May 2, 2014 at 2:26

3 Answers 3


OpenBlocks Liquid XP has two big advantages: first, it stores 50 XP/bucket compared to LXP's 10; second, if you put it into an OpenBlocks tank, you can right-click with an empty hand to instantly consume enough XP to gain one level. LXP requires you to use a Fluid Transposer to put the XP into Bottles O' Enchanting in order to gain levels.

  • He's asking for difference between Mob Essence and Liquid XP... Commented Jun 15, 2014 at 13:49

So why not do testing? With this setup:here
we can tell that each kill with the grinder gives 666mB of mob essence. Now when we switch to openblocks, we get this which produces ~50mB of Liquid XP.(Sometimes more, sometimes less) Now let's convert that to Mob essence:here. With our first kill, we got 664mB of Mob essence! That is 2mB less that the Grinder method. So we will stick to the MFR method. What if we want to convert it back? We use an auto-enchenter(Yeah, that sucks). If you place glass bottles inside, you get XP bottles. So with the 666mB of mob essence, we only get 1/2 bottles. This means that to produce 1 bottle of XP, we need 2 kills with the grinder. With the Openblocks setup, we also needed ~2 kills. So which method to use it up to you. To answer your question, lets do more testing. We will put a book in the auto-enchanter. We need 25 zombies to get a level 30 enchant on the book and we get 138 mob essence remaining. Now with the openblocks setup, we need 27 kills to get the enchant. (Using XP-MobEssence) With the OpenBlocks enchanting table, it takes around a lot more kills. So, I would recommend using the MFR Grinder method.


Mob Essence gives 1 level per drink but requires you to drink with a straw, which I personally find annoying and Liquid XP gives 1xp point per 20mb which will give you 1 level each click on the tank but because the amount of xp needed per level increases if you have no xp at first you will get 3.5 to 4 levels out of 1 bucket but later down the line if you have 29 levels going to 30 you will need to consume over 1 bucket worth

For level 30 enchanting; The MFR auto enchanter needs 28.6 buckets of mob essence which is just under 30 levels vs the exact 30 buckets of liquid xp required for the Auto Enchantment Table from open blocks

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