Adamantine Weapons

[gamedave]

So, several members of the party now have adamantine weapons, just in case they run into a construct that's resistant to non-adamantine weapons. Funny thing - unlike previous editions, 5E has no rules for adamantine weapons, other than mentioning them in the stat blocks of some constructs. Adamantine armor, yes. Weapons, no. Not even a price. So, here's my house rule:

ADAMANTINE WEAPON
Weapon (any melee weapon other than club, greatclub, or quarterstaff; dart; any ammunition), uncommon
This magical weapon is reinforced with adamantine, one of the hardest substances in existence. When you attack a non-adamantine object with an adamantine weapon, any normal hit becomes a critical hit.

[Moose Jockey]

Does this include weapons and armor?

[gamedave]

D&D Next doesn't really have a system to handle sundering weapons and armor, only unattended, inanimate objects. As a quick fudge, I'd probably say you could target a worn or wielded object with Disadvantage, using the higher of the target's AC or the object's inherent AC (DMG, Chapter 8, "Objects", p. 246-7).

[gamedave]

The fact is, as mentioned above, D&D Next just doesn't have official rules for adamantine weapons, but does mention them in a couple of construct entries, and you guys spent in-game resources to acquire some, so I wanted to come up with rules for them to do something. Even without extra object damage (or sundering weapons and armor), they still count as magical weapons.