This horror mod adds Leggy 000145236 to your game long legged steve with no face, it's an entity that will spawn randomly in world and will hunt you or sometimes attack, acts like dweller also it can leave signs with creepy messages
If you mange to kill it, you have a chance to get Leggy Fragment, by obtaining three of these you will be able to craft Anomaly Detector with four iron and two redstone, when in hand, this device will start beeping if Leggy is nearby you of 70 blocks
You can adjust Leggy's activness by going to your game folder game\config and find file called "leggyspawn" open it with notepad and change the value, default is 0.008, change it only between 0.001 and 0.009
Craft anomaly detector
