The Chain Tower and the Iron Stalker

The Chain Tower

This room is circular, very tall, and quite narrow (40' tall x 10' diameter).
From the ceiling dozens -maybe hundreds- of heavy chains are hanging at 8' from the floor, moved by an imperceptible breeze and filling the room with an incessant clinking sound. The chains are so many they literally fill the area and it's nearly impossible to see anything and it's incredibly difficult to move through them.
There are three doors in the room, at 20', 30' and 40' of height from the floor, all hidden in darkness and by the chains. These doors are the only way in and out.

This room can be used as a sort of puzzle by itself, or can be used in conjunction with the Iron Stalker.

The Wall Of Hanging Chains by Allan Swart

The Iron Stalker

The subtle (but noisy) movement of the chains is not made by actual breeze, but by the light breathing of the creature silently hanging from them on the very top of the room.
It is a grey, gaunt and anthropomorphic creature, with bulging -and now nearly useless- eyes and a patch of long rust-reddish hair on the head.
It has two long and strong arms it uses to move and hang on the chains, but the creature can use its legs and feet just as well.

It feeds on iron and rust, but it cannot chew metal and for the last hundred years the creature stayed alive by patiently licking and sucking the chains, absorbing the iron by slowly consuming them.
The Iron Stalker is in fact incredibly attracted by iron, and the only reason it never left the room is because of the huge quantity present in it.
Because of its nature, this creature only receives half damage by iron and steel weapons.
Its blood is dense like melted iron, but cold, and its color is a twirling mix of iron-gray and rusty-red.

Iron Senses

The Iron Stalker cannot really see in the dark, but it can see the iron. Also, anything that has no iron in it (like wood) loses the interest of the creature, and it will pay less attention to it.
This makes the Iron Stalker harder to be hit with iron or steel weapons, but easier to be hit by weapons that have no iron.
Any mundane animal (included humans and demihumans) have the right amount of iron to not be in advantage nor disadvantage when fighting the Iron Stalker with their bare hands/claws/jaws etc.

The Iron Stalker's sense of smell is incredibly refined for iron but it's way less developed for other molecules.

Behaviour

As soon as someone or something made of flesh and bone enters the room, the Iron Stalker can immediately smell the iron in their blood and begins to desperately crave it (obtaining iron by drinking blood is far easier than sucking it from an item or from ore, and it's also tastier).
But the Iron Stalker is cunning, and knows how to plan, how to wait, and has learned how to hang from the chains and how to move between them with the least effort.
It will, if possible, wait for the victim to move between the chains in order to climb down causing the least suspicion, and if safe enough it will suddenly put a chain around the target's neck, snatch them up, and quickly climb to the top of the room.
Once there, it will finish to strangle the victim with the chain and then will proceed to cut its throat and drink its blood, absorbing the iron in it.

Iron Curse

Whoever is touched by the Iron Stalker must Save vs Magic to avoid being cursed. If the victim is instead bitten, no Save is allowed.
The Iron Curse causes the same symptoms of extreme iron deficiency (check them out) and it will last one week unless removed by a Remove Curse spell.
The accursed will be extremely fatigued, weak and dizzy, they will suffer from speech impediment and will have a poor appetite towards actual food but at the same time they will crave non-nutritive substances, such as ice, dirt, starch or more often than not, iron and rust and they will try to eat them if not restrained.

Undead Zombie Concept Art by Karl Lindberg

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The Iron Stalker

Armor
- AC 20 (as plate and shield) and suffers half damage against iron or steel weapons.
- AC 12 (unarmored) against weapons with no iron on them.
- AC 16 (as chain) against all other weapons.
Hit Dice 4
Hit Points 20
Movement 120'
Morale 6
Attacks: 2x Iron Claws -or- Bite -or- Strangle

• Iron Claws: 2 attacks on a single target, 1d6 damage; on a damage roll of 6 the target is Strangled. A successful attack may cause the Iron Curse (Save vs Poison to be spared).
• Bite: 1d6 damage; a successful attack causes the Iron Curse (no Save allowed).
• Strangle: automatic if attacking with surprise from the chains (no attack roll needed); every round Save vs Paralysis or suffer 1d8 damage (on 1st success no damage is suffered, on 2nd success target frees themselves); target cannot otherwise act.

The Iron Curse

• Attacks and Saving Throws are rolled at -4, Reactions at -2, Skills at +1.
• When casting spells the character must Save vs Magic to avoid a Miscast -or, if you're using the traditional spellcasting system- the spell fails and its casting cannot be attempted anymore unless prepared again.
• The character will not eat normal food (possibly suffering the effects of Starvation), instead they will try to eat other possibly dangerous non-nutritive substances as per description.