Napstablook from Undertale. They have a small chance of spawning during the night on the ground. If you bump into them, A fight will occur. They will fly upwards and shoot tears at you until you go away. They have 40 hp, but are fairly difficult to kill, as they shoot tears at you relentlessly. This mod is still in development, so let me know if you have any issues!
Minecraft Forge mod
Latest supported Minecraft version