NDS Mobs

NDS Mobs are Non-Despawning Mobs. They are varients of hostile mobs that won't despawn after moving a certain distance away.

Their primary use is for Adventure Maps that contain dungeons or rooms where you only want a certain amount of mobs. I found when I was making adventure maps in the past that I would sometimes want a room where you had to kill a certain amount of mobs before you could proceed and I either had to keep respawning the mobs if the player died or the mobs would just despawn and it would break what I wanted to happen.

This way, a player can trigger the spawn and die as many times as they want without the mobs ever disappearing.

The description on the Spawn Egg tells you that it's Non-Despawn.

There are currently these NDS Mobs:
 * Zombie
 * Skeleton
 * Wither Skeleton (It has it's own egg, so you can spawn it in the Overworld)
 * Creeper
 * Spider
 * Cave Spider
 * Blaze
 * Zombie Pigman
 * Ghast
 * Silverfish
 * Witch
 * Slime
 * Magma Cube