Turns Minecraft into an idle-game (kind-of, not really). Gain xp and generate items on servers (and in singleplayer), that works even while you're not playing. Perfect for those with not a lot of time on their hands.

To begin, craft the Replication Device. (Get JEI/REI/EMI !) When you place it down, it will do nothing at first. Insert any fuel into the fuel slot (below the fire icon), and press the record button. You can see how long it will stay active at the top of the device's inventory panel. Now, you can toss items nearby, and the Replication Device will consume those items and store it in its memory.

Normally, you will have to wait an hour for the process to finish. But you might have noticed a skip button. After waiting for a minute, the skip button becomes active. DON'T PRESS IT YET. You can craft an Extrapolator Module, then put it in the Extrapolator slot above the Fuel slot. Doing this, and then pressing the skip button will take the current time that has passed, and the items gathered, and multiply the current rate of items to be generated by up to 60. (If you press it right on the dot). It will end the recording phase, and start generating items.

When it begins generating, you can withdraw items by pausing it, and resume it to Replicate items again. The Replication Device will collect items that are simple. It can not pick up items that have NBT tags attached. If you feel rates are too slow, you may Re-record. It will ask for a confirmation, just in case you click it by accident.
Doing so will clear all recorded items. It's this mod's version of a Prestiege system in idle games.

The experience gain works passively without needing to craft the Replication Device. By default, you gain 1xp/min, for every 100 zombies, 100 skeletons, 100 creepers, etc. You can balance these values in the config.

And yes, players will still be able to gain xp and loot while offline.

Idle-ify