Is there a mineral/metal with anti-magic properties in D&D?

[Dungeoneer]

@Dungeoneer
Yep, definitely can make up my own. As @WayneLigon points out, however, there could be far reaching consequences to introducing an anti-magic material. What would be reasonable properties to give it that didn't invite serious exploitation?

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@Tony Vargas
Hah! To clarify, in my adventure, it's not important the PCs lose the ability to cast magic, rather it's important that the beholder-like creature is having difficulty with its magic abilities...and since it's underground in the Outlands a sensible interesting way to explain that would be an anti-magic mineral. Also, while I like the idea of cold iron, since this is a D&D adventure that would expand what cold iron does a bit too much beyond tradition/expectation.

Are there non-magical planes? I'm not really familiar with the Great Wheel. But presumably if there was one it could be intruding on this region.

I think any anti-magic material is going to present the problem of "why don't people use it all the time."

Could also be the result of some kind of nearby artifact.

 

[Nagol]

[MENTION=20323]Quickleaf[/MENTION], did you need an OGL option or is closed content fine?

 

[Quickleaf]

Are there non-magical planes? I'm not really familiar with the Great Wheel. But presumably if there was one it could be intruding on this region.

I think any anti-magic material is going to present the problem of "why don't people use it all the time."

Could also be the result of some kind of nearby artifact.

Quick tidbit about the Outlands from the 1e Manual of the Planes:
[sblock]The First Edition Manual Of Planes states that the center of the plane takes various forms at different times (a mountain, a huge tree, etc.) and godly powers are lost as one moves toward the center, as well as spells, beginning with the highest levels of spells at the farthest out and then gradually losing the lower ones step by step the further one moves inward. Within 100 miles (160 km) of the center, not even chemical reactions take place, and neither man nor deity can get closer than 100 miles (160 km).[/sblock]

That's true that if it can be mined and used broadly, then it could unbalance the game. Maybe I can come up with a device that explains how it was a failed mining venture (the property of the mineral fades soon after extraction). That way it becomes more an environmental property than something that can be arrived around and used.

[MENTION=20323]Quickleaf[/MENTION], did you need an OGL option or is closed content fine?

I'm curious to hear about the closed content, yes, but if/when I decide to turn this into a published product, then obviously I'd be going OGL.

 

[Tony Vargas]

Well if the underground area is near and leads to that center, there you go. It's powers are being leached off that way. The eye-rays are mostly equivalent to various-level spells, or you could ballpark a level. Levitation's only level 2 (though the Beholder's is better, though not as good as level 3 fly), so it'd go last.