What difference does it make for a weapon to be made of adamantine?

  • I'm wondering about the differences between metals when it comes to weapons in D&D. For example, if I have a Steel Dagger and an Adamantine Dagger, what would be the difference between the metals besides weight and hardness?

    I don't see where in the DMG or XGE it states that the weight of adamantine armor or weapons differs from that of the regular variety.

  • Armor

    The Dungeon Master's Guide tells us about Armor on page 150.

    Adamantine Armor

    Armor (medium or heavy, but not hide), uncommon

    This suit of armor is reinforced with adamantine, one of the hardest substances in existence. While you're wearing it, any critical hit against you becomes a normal hit.


    There is more information about Adamantine Weapons in Xanathar's Guide to Everything on page 78:

    Adamantine is an ultrahard metal found in meteorites and extraordinary mineral veins. In addition to being used to craft adamantine armor, the metal is also used for weapons. 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 a critical hit.

    The adamantine version of a melee weapon or of ten 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.

    So, it affects hardness, weight, cost, and damage. Adamantine armor turns critical hits against the wearer into regular hits; any hit from an adamantine weapon against an object does extra damage because it's a critical hit.

    Automatic critical damage *to objects*.

    @TuggyNE Good catch.

    The last paragraph states that it affects weight, but nothing quoted above that mentions weight.

  • Adamantine is mentioned three times in the DMG (excluding tables):

    • Page 150:

      Adamantine Armor

      Armor (medium or heavy, but not hide), uncommon

      This suit of armor is reinforced with adamantine, one of the hardest substances in existence. While you're wearing it, any critical hit against you becomes a normal hit.

    • Page 161, explaining that Daern's Instant Fortress is made out of it.

    • Page 246, where objects made of it have an AC of 23. This compares with 21 for mithral and 19 for steel or iron.

    As yet, there are currently no rules for Adamantine weapons but they are coming in Xanathar's Guide to Everything.

    I would also mention that, in the MM, many Constructs have an Adamantine Bypass on their damage resistance.

    *Xanathar’s Guide to Everything* is now out, so this answer is out of date and should be updated.

  • Special materials like that are explained in the Dungeon Master's Guide.

    In short, objects made out of adamantine have a higher AC. Armor made out of it negates critical hits. And weapons made out of it can damage monsters that have damage immunity to weapons that aren't adamantine.

    The Adamantine Armor in the DMG is a magic item. There's no way to tell that negating critical hits is a property of the armor as opposed to magic.

    @Doval whether or not the magic is inherent in the metal, or is a byproduct of forging things from the metal (it takes magical aid to mundane forging) is a detail not provided in the 5e material I have reviewed.

  • As others have said, adamantine weapons don't currently do anything except bypass certain kinds of damage reduction. However, on page 246 of the DMG, it says you can give objects immunities, resistances, or vulnerabilities based on specific damage types.

    In prior versions of the game, Adamantine weapons ignored hardness, and while hardness isn't a thing anymore, you could certainly decide that, based on that, all non-adamantine objects are vulnerable to damage from adamantine weapons.

    Alternatively you could have an adamantine weapon automatically deal maximum damage to objects, and then apply vulnerability or resistance based on specific damage types (such as applying resistance if you're trying to stab a door down, since it's just not a very effective way to go about the task).

    In either case, the adamantine weapon should not take damage from being used that way, while steel or other materials might.

  • I've ruled in my games that adamantine armors have slightly higher AC along with the critical hit negation. For Adamantine weapons i rule they add a +3 to damage as well as bypassing non magic weapon resistances. I make adamantine items really rare in my games so it's a good bonus and it is fun to see 2 characters fight over one when they both have the proficiency for it.

    Can you give a rules source for Adamantine having these benefits? I can't seem to find them in the 5th edition source books?

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Content dated before 6/26/2020 9:53 AM