Adamantine Weapons and Armor 5e: How It Really Works & Homebrew Options

Adamantine – along with mithril (or mithral), unobtanium, vibranium, etc. – has a long established place on long lists of materials beloved by fantasy and science fiction writers.

You probably know it as Adamantium: the material grafted onto Wolverine’s skeleton and retractable claws. Snick. 

Sword of Feast and Famine
© Wizards of the Coast by Steven Belledin

In whatever form it crops up throughout comic books, movies, and novels, adamantine is a byword for strength and nigh-unbreakable toughness.

In Dungeons & Dragons, the story is very much the same, and an adventurer wielding an adamantine weapon or clad in adamantine armor is undeniably a force to be reckoned with. 

Adamantine in DnD

In Dungeons & Dragons, adamantine is a rare metal that crops up in various forms throughout the history of the game and its various worlds.

There are also several alloys of varying purity, including adamantite, adamant, and adamantium. 

Adamantine in D&D looks very different from its more well-known counterpart in the X-Men comics.

It’s a jet-black metal that shimmers green under torchlight and purplish white under magical light.

This, in all honesty, was probably a conscious decision aimed at distinguishing adamantine from Mithral, D&D’s other legally distinct fantasy metal. 

The mad beholder, Xanathar, notes that adamantine ore is found in meteorites and extraordinary mineral veins.

Dwarves (or Svirfneblin, the deep gnomes) are likely the only folk ever to mine it, let alone have the skill to forge it into anything useful, although some powerful spellcasters (including the arch-lich Acererak, who famously made a door of solid adamantine to bar entry to the Tomb of Horrors – which was obviously stolen by the next adventuring party to roll through) also use it to craft magic items or fuel their arcane research.  

Adamantite: The naturally occurring ore from which adamantine is refined.

Adamant: An extremely hard but brittle metal refined from adamantite ore. Often stated to be the pure form of the metal that must be worked to produce adamantine. It is surprisingly light.

Adamantium: A rarely used, less legally safe from the suits at Marvel, synonym for adamant.

Adamantine Weapons in DnD 5e 

The rules for adamantine weapons were officially introduced to D&D 5e as part of Xanathar’s Guide to Everything and, honestly, are a bit strange. 

Melee weapons and ammunition made of or coated with adamantine are unusually effective when used to break objects.

Whenever an adamantine weapon or piece of ammunition hits an object, the hit is considered to be a critical. 

Note that adamantine weapons have no different effects when it comes to attacking creatures, but there are few doors or castle gates in the multiverse that could withstand a blow from an adamantine battering ram.

Still, for adventurers who spend their time in the dungeons beneath castles rather than trying to storm the gates with an army, this effect scarcely justifies an adamantine weapon’s price tag. 

The adamantine version of a melee weapon or of 10 pieces of ammunition costs 500 gp more than the normal version, whether the weapon or ammunition is made of the metal or coated with it.

Of course, finding a smith who can successfully work with adamantine is likely to be no small feat in and of itself. 

While adamantine weapons are not inherently magical (a +1 adamantine longsword is just a very good sword), they are still effective in overcoming damage resistances displayed by some creatures – specifically constructs. 

Animated statues, gargoyles, stone golems, and their ilk commonly have resistance (or even immunity) to all Bludgeoning, Piercing, and Slashing damage from nonmagical sources.

But many of these monsters, like the Giant Four-Armed Gargoyle from the Tomb of Annihilation, specifically note that adamantine weapons overcome these resistances. 

House rule alert!

Personally, I really like the idea of adamantine weapons being effective against constructs and inanimate objects, but I don’t think the rules go far enough. At my table, adamantine weapons… 

  • Overcome all resistance to Bludgeoning, Piercing, and Slashing damage. 
  • Deal an additional damage die of the weapon’s type against Constructs. 
  • Any damage dealt to a target wearing nonmagical metal armor (or natural armor dealt to stone) can instead be dealt to the wearer’s Armor Class in place of damage. The target’s AC cannot be reduced to lower than 8 in this way. 
  • Adamantine ammunition can only reduce a target’s AC by 1 point per successful hit in exchange for dealing half damage to the target. 
  • Are brittle. Rolling a 1 on an attack roll with an adamantine weapon or piece of ammunition destroys the weapon or ammunition. 

I think this tweak justifies the massive price point for adamantine gear but also introduces a fun limitation that means while adamantine weapons are now situationally very powerful, a character probably wouldn’t want to use an adamantine sword as their first and only choice of blade. 

Basically, I like the idea that characters who take the time to research and prepare for a specific enemy should have a noticeably easier time of it. It’s probably all those hours I spent playing Witcher 3

Adamantine Armor in DnD 5e 

Armor (or shields – this isn’t specified in the rules, but I’d allow it) forged from adamantine is almost totally impervious. 

By reinforcing a suit of armor with adamantine (noted to be one of the hardest substances in existence), the wearer treats any critical hit against them as a normal hit.

That is… mechanically huge. 

Adamantine can be used to reinforce the following types of armor. 

NameTypeACStrengthStealth
Chain ShirtMedium13+ Dex modifier (max 2)
Scale MailMedium14+ Dex modifier (max 2)Disadvantage
BreastplateMedium14+ Dex modifier (max 2)
Half PlateMedium15+ Dex modifier (max 2)Disadvantage
Ring MailHeavy14Disadvantage
Chain MailHeavy16Strength 13Disadvantage
SplintHeavy17Strength 15Disadvantage
PlateHeavy18Strength 15Disadvantage

Seriously, I cannot overstate just how powerful being able to ignore all critical hits against you can be.

A suit of adamantine armor is so useful it’s verging on a requirement for any tanky frontline.

Definitely something a paladin would go on a long, grueling quest to get their hands on.