Name of Mob: The Mandragora Helix

 Description: An entity that might attack when you travel in your TARDIS

 Lore/Brief Background: It is an ancient creature that existed before our universe. In this universe, it is a large energy spiral with rings and a ball of energy in the center. The Fouth Doctor and Sarah Jane Smith encountered it in The Masque Of Mandragora.

For more information, check these links:

Escaping the Mandragora Helix

The Helix possesses a cult in 15th century Italy

Wiki article

 Behaviour:

• How it attacks players: It attacks the player when he/her is in the TARDIS. It damages the TARDIS bit by bit unless the player pilots it through the center.
•   While piloting, the player also has to complete a simple task such as saying the alphabet backwards or naming mobs. Otherwise the helix successfully controls you. (As in the episode)
• Once the player gets in, he has to battle a ball of Mandragora energy. It may also get into the player's TARDIS and get out after the player lands
• While the Mandragora energy is being attacked, it may summon the brothers of Demnos from the episode. They are from 15th century Italy, but it would be impractical to add another dimension.
• Spawning(Biomes/dimension, spawn rate): It sporadically attacks while the player is in the TARDIS dimension. Maybe it attacks once every 1000 travels?
• Nature (Hostile/Passive/Neutral): Hostile
• Anger Triggers: Random while the player is in the TARDIS
• Special Traits: It appears as a spinning energy spiral and the mandragora energy inside appears as a flying red ball
• Drops: It could drop multiple Nether stars? I dunno, it didn't drop anything after being defeated in the episode
• Abilities: Summoning Brothers of Demnos
• Notable weaknesses: The attack damage can be absorbed by wearing metal armour like steel or iron. That is how the Doctor weakened the helix in the episode

Why should this be implemented: It could be a very strong and interesting end-game boss in the game

Image(rough sketch/draft acceptable):

Brother of Demnos (This is their leader, Hieronymous)

The helix (With TARDIS going through):

Center of Mandragora Helix:

Hieronymous with Mandragora energy:

Any other information:

Health: Maybe 500 for the Helix and 40 for the Brotherhood of Demnos?

5000 health especially, and 100 health are excessive to the highest degree. Having to recite the alphabet backwards would be tedious, I like this suggestion, but this would get very annoying.

Besides what Ford said, having it be every 100 travels would be annoying. Maybe a 1/1000 chance when changing coords/planet?

 Well I guess I'll reduce the health, as for the tasks, it's just to stick to the show, it's for resisting the helix's control.

 Yeah, maybe, it is end-game after all

So, first question, is this in any dimension?

 Well I intend for the piloting part to be in a sort of GUI/view like when you use the flight panel, I guess in a 'mandragora' dimension? As for the battle in the center I guess it'll be in another seperate dimension.