D&D Monster Monday: Iron Cobra

D&D Monster Monday Iron Cobra

Suddenly the giant, metallic snake statue springs to life as you approach it. It lets out a terrifying hiss and slithers toward you. Before you can raise your shield you feel its fangs pierce your flesh, a strange poison seeps into your bloodstream. You can’t move. It rears its head back for another bite, aiming straight for your jugular.

I recently had the opportunity to use an iron cobra. I’d never heard of this creature before using it. While it wasn’t super effective against the group I used it on, it’s an interesting creature with a cool randomized bite mechanic.

Statues of snakes are already terrifying. I mean, if you see a bunch of iron snakes in a hallway, you know somethings up. To have one spring to life and attack you with its poisonous fangs is the icing on the shit cake.

With that in mind, let’s slither into Mordenkainen’s Tome of Foes to learn all about these reptilian constructs.

an iron cobra with golden accents
I love the 5e artwork for the iron cobra. It’s by far my favorite version of the creature. Credit: WotC.

Iron Cobra Lore

An iron cobra is a metal snake. That’s it.

How it’s made, however, is where all the cool lore info is.

Iron cobras are one of many types of gnomish constructs. They are clockwork constructs that are loaded with alchemical concoctions that function similarly to snake venom, albeit with a variety of effects.

Clockworks are fantastic creatures to use as guards since they do not require air, food, drink, or sleep. They can sit in their designated zone and guard it until they’re destroyed.

Iron Cobra Stats and Abilities

You can find the iron cobra’s statblock on page 125 of Mordenkainen’s Tome of Foes.


Size: Medium construct
AC: 13
HP: 45 (7d8 + 14)
Speed: 30 ft.
STR: 12 (+1)
DEX: 16 (+3)
CON: 14 (+2)
INT: 3 (-4)
WIS: 10 (+0)
CHA: 1 (-5)

While 13 AC and 45 HP aren’t impressive for a CR 4 creature, fret not. The iron cobra has quite a few defensive perks that help to offset these.

Their ability scores are decent as well. They’re Dexterity-based attackers so their +3 modifier will come in handy. Plus, this respectable modifier also helps them defensively with regards to their AC.

Due to their high Dexterity and decent Constitution, they’re in a good spot for the three common saving throw abilities. Plus, their Magic Resistance will also give them a boost in this department.

Their Intelligence and Charisma are both abysmal, but this isn’t anything to worry about. These are not frequently-used abilities in the majority of scenarios.

Resistances, Immunities, Saves, and Skills

Skills: Stealth +7
Damage Immunities: poison; bludgeoning, piercing, and slashing from nonmagical attacks that aren’t adamantine
Condition Immunities: charmed, exhaustion, frightened, paralyzed, petrified, poisoned
Senses: darkvision 60 ft., passive Perception 10
Languages: understands one language of its creator but can’t speak
CR: 4 (1,100 XP)

+7 to Stealth is a massive bonus that you would be foolish to not make use of. Iron cobras are phenomenal ambushers. Plus, due to their appearance, you could easily have them hide in plain sight, disguised as statues.

They have immunity to four of the most common damage types in the game. Although that’s provided that the party doesn’t have magical weapons when they confront the iron cobra. Realistically, it’s not guaranteed that they would, especially if they’re squaring-up against CR 4 creatures.

Their condition immunities are your run-of-the-mill construct immunities. Still, these make an already hard to crowd control creature, more difficult to lock-down.

While their passive Perception is nothing to write home about, 60 ft. of darkvision will be useful if you use them as a guard or an ambusher.

CR 4 is a reasonable rating for them, although they’re difficult to judge due to the high-variance of their offensive action.

Traits and Abilities

Magic Resistance. The iron cobra has advantage on saving throws against spells and other magical effects.

Magic Resistance is such a powerful trait. This helps to shore-up their weakness in Wisdom saving throws while making their Dexterity and Constitution saving throws that much stronger.


Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) piercing damage. If the target is a creature, it must succeed on a DC 13 Constitution saving throw or suffer one random poison effect:

  1.  Poison Damage: The target takes 13 (3d8) poison damage.
  2.  Confusion: On its next turn, the target must use its action to make one weapon attack against a random creature it can see within 30 feet of it, using whatever weapon it has in hand and moving beforehand if necessary to get in range. If it’s holding no weapon, it makes an unarmed strike. If no creature is visible within 30 feet, it takes the Dash action, moving toward the nearest creature.
  3.  Paralysis: The target is paralyzed until the end of its next turn.

Bite is a very interesting action. Its +5 to attack is decent, but its average of 6 piercing damage is god-awful.

However, if the target is bitten and fails a DC 13 Constitution saving throw they’ll be poisoned in one of 3 different ways. Either the target takes an additional 3d8 poison damage, attacks an ally, or is paralyzed until their next turn.

Keep in mind, this effect is random so you can’t plan which poison the target is affected by. Thankfully, however, all three of these effects are super useful.

The damage takes Bite’s damage from abysmal to significant.

Confusion waste’s the target’s action economy while inflicting decent damage on a different ally.

Paralysis sets up the target to take massive damage from the iron cobra’s foes while wasting their entire turn.

Iron Cobra Strengths

Plentiful Crowd Control

Two out of the three poison effects are some flavor of crowd control.

Confusion void’s the creature’s turn and instead forces them to attack a random creature within 30 feet of them. This may also force them to move up to 30 ft. toward the chosen creature, providing some movement displacement.

While this could force the target to attack one of the iron cobra’s allies, there’s still a decent chance that the target may turn on their own friends. Plus, it forces them to give up their action on their turn which is some powerful crowd control in its own right.

Paralysis is pretty self-explanatory. It renders the creature unable to move or use any of its actions on its turn. Plus, any attacks against the creature are made at advantage and deal critical damage if it’s a melee attack.

It paints the paralyzed creature as a juicy target for all of the iron cobra’s allies.

Iron Cobra Strengths
Snakes are scary in general, but metal snakes? Count me out. Credit: WotC.

High Potential Damage

The iron cobra has the chance to deal 19 average damage to a single target with each Bite. Provided that the target fails their Constitution saving throw.

That is a huge chunk of damage, and while it’s not guaranteed, is still something to make note of. The iron cobra’s damage output goes from 0 to 100 really quick!

High-Value Damage Immunities

45 HP isn’t impressive. In fact, it’s weak for a CR 4 creature.

However, that 45 HP becomes much more impressive when it’s backed by immunity to four of the most common damage types in 5e.

Nonmagical weapons that aren’t adamantine are rendered useless against these creatures. A plethora of poison spells and cantrips will be ineffective.

These creatures don’t need a large health pool simply because there are so many different attacks that won’t affect them.

Iron Cobra Weaknesses

High-Variance Creature

The iron cobra a ton of crowd control and damage built into its Bite. However, due to the effects being entirely random it isn’t the most reliable creature.

You may need the additional poison damage but roll for paralysis instead. Sure, it’s still useful, but you can’t bank on getting any specific effect. This means you need to be adaptable in your strategy since each effect will change how the rest of your combatants’ tactics.

Not to mention that these effects only take place if the target fails a DC 13 Constitution saving throw. While this isn’t a freebie save, it’s not a difficult one to beat. This also makes the creature less effective at higher levels.

It’d make a great minion creature for high-level adventures, but the low DC holds it back in this regard.

How to Play an Iron Cobra

Pair it With a More Consistent Creature

While we can’t make the iron cobra more consistent without homebrewing them (potentially changing their identity). One way to make them into a more consistent encounter is to pair them up with consistent creatures.

Creatures that deal an average amount of damage in an average way.

The good thing is, the Monster Manual and other books are full of such creatures. It won’t be hard to find a couple to throw alongside an iron cobra.

This ensures that there’s an ever-present threat to the party even when the iron cobra doesn’t dish-out extra poison damage or the target makes the save against their poison.

Plus, it makes the iron cobra’s paralysis poison more useful as other creatures can tag in and deal massive damage to the paralyzed foe.

Surprise Attack!

+7 Stealth is such an enormous boon to the iron cobra’s statblock. Socking a few iron cobras away in dark crevices or hallways of underground dungeons, laying in wait to ambush unsuspecting adventurers is a fantastic way to give these creatures some extra juice in combat.

Plus, thanks to their construct tag, they don’t need to eat, sleep, drink, or breathe so they can sit in their ambush point indefinitely.

Only the most perceptive of adventurers will be able to spot these creatures. Ergo, it’s worth your while to have your iron cobras hide and strike when the time is right, buying themselves some extra time.

5 Iron Cobra Plot Hooks

  1. Guardian of the Treasure – The treasure room of the dungeon is lined with statues of metallic creatures. Cobras, elephants, wolves, monkeys, and other creatures stand vigilantly, staring at the wealth of treasure in the center of the room.
  2. A Gnomish Mastermind – Rumor has it, a gnome engineer has created a more potent syrum to insert into an iron cobra. They refuse to say what effects it has, although that’s implying that they know what their invention does in the first place.
  3. Missing Guardian – A shipping tycoon purchased a few iron cobras to use as guards for their warehouses in the city. Strangely enough, one seems to have malfunctioned and has been missing for a few days.
  4. Get Me More Parts! – The engineering guild is running low on clockwork parts. Unfortunately, they just accepted a rush order of constructs. They’re offering a high price for someone to trek the dangerous mountain path to the gnome city to procure enough parts ASAP.
  5. Aquatic Modifications – A famed inventor unveiled his latest work. Amphibious iron cobras! However, once they leapt into the water, they never returned to him.


All in all, the iron cobra is a formidable foe, albeit a high variance one.

Their statblock has a ton of great goodies baked into it. Crowd control, high damage, valuable damage immunities, stealth, and hardy saving throws. They’re a swiss army knife of a creature.

Although they’re not totally reliable. Their high variance is both a blessing and a curse. Sometimes your poison may give your creatures what they need, other times it might not work out so well. Still, at least every effect is beneficial to some degree.

The gnomes know what they’re doing with regards to clockwork. These iron cobras are scary creatures for sure!

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