The End is pretty bland. I propose we change that by adding some new challenges.
The Twitcher is a humanoid mob about the same size of a player, but much lankier and deformed. When it moves, it Twitches, hence the name. They spawn commonly in those large rooms in End Cities, and more rarely in the Outer End itself, about as rare as a Witch.
The Twitcher moves by crawling over the floor, as it cannot support itself as long as it is not latched onto a Minecraft player.
You read that right. As soon as a Twitcher spots you, it will slowly start stalking the Player, hungrily. After approximately 14
months seconds, it will suddenly pounce on top of the Minecraft player, and attach itself to the Minecraft player. Once attached, there is no way to remove a Twitcher for the Minecraft player. They're stuck with it until they leave the End.
The Twitcher doesn't really cause any damage, but it obscures your vision and slows you down, so it is mostly an unnecessary hassle the Minecraft player will have to deal with until they stop playing.
I reskinned a Zombie in MS Paint to give you an idea of what a Twitcher looks like.
Please leave any comments to add to or improve my idea. Constructive criticism is heavily
Edit 1: as CosmicjLightning pointed out I forgot to give this abomination of the End some health. Because of their annoying tactics, and generally cowardice way of behaving, I'd figure they don't have a very high health stat. This would also give Minecraft Players a chance to fight off a Twitcher before it strikes them, though it will still latch onto unsuspeting Minecrafters, or people who don't care about it being there.
I'd say 8 health points, or 4 hearts of health is fair. That's half as much as a Spider's health, for reference.
Edit 2: Courtesy of yoshi9048, you will also be able to remove a Twitcher that has attached itself to you by setting yourself on fire. The warmth of the fire and the bright light is enough to scare away a Twitcher, which feels most at home in cold, damp darkness.