The Professional Killer

Professional Killer is a green mob with a displeased face that fights living creatures such as animals, villagers, illagers and players, but leaves other mobs alone. When it dies it drops its heart, which can be combined with other materials. The mod also adds a Stone Beach biome and a new biome called Dread Forest, reached through a flower found in a Mushroom Forest biome. Crafted armor based on the mob is cosmetic only, so mobs keep treating the wearer as a normal target.

The mod is built around a nightmare version of the mob. Crafting a Captured Evil block from Soul Sand and the Killer's heart, activating it, and summoning the nightmare version brings back a smiling, bloodied creature that attacks everything it sees. Its defeat drops a Heart Evil. Hits from the mob can hurt the player directly, which is why iron combined with the heart is recommended as cover. The Heart Evil does not damage the holder and combines with a flower into a Sword Power that uses evil magic and redirects undead mobs.

Environment is client and server, so the server and every player need the mod. Files are published for Forge only, for Minecraft 1.12.2. The license is MIT License, and the mod is not open source.