If you are trying to make custom minecolony structures that include Immersive Engineering pipes or conveyor belts you will notice a very ugly nullpointer exception crash.
This mod is an addon for IE that uses asm transformation to inject the following code (simplified) into fluidpipes and conveyorbasic and conveyorvertical:
if (getWorld() == null) return {returnvalue};
This will prevent the nullpointer crash.
You only need this mod if you are trying to make custom structurize structures that include pipes / conveyor belts. If you do not want to make custom structurize structure with IE pipes / conveyor belts, this mod will do nothing for you.
Of course it would be way easier to just add the code directly into IE but sadly, the authors refuse to publish a new build so we have to use this.