In my last post, I mentioned using Phase to stop meteoric iron arrows*. William Knowles responded with a "Huh."
Meteoric iron says it is "immune to magic - Reverse Missiles, Steelwraith, Turn Blade, and so on won't stop it, and Shape Metal, Shatter, and the like can't destroy it."
Otherwise, there isn't much in the books to say what meteoric can and can't effectively do by being immune to magic.
What do I let magic do against it?
You can use any Blocking spells that either work on the attacker (Command is a good choice, so is Fumble) without affecting the weapon, or on the caster without affecting the weapon (Iron Arm won't work, nor will Turn Blade, but Phase and Blink will.)
Essentially, as long as the magic is either getting the attack out of your way without affecting the meteoric weapon directly, or getting you out of the way, it's probably okay.
Ah, but you might say. Steelwraith is on the caster, not the item! But it's effect is a) specifically called out by meteoric, and b) it's not the same as Phase. Steelwraith is an Earth spell with Walk Through Earth as a prereq, and meteoric is clearly there to stop people from just ghosting through it to bypass barriers.
Phase is a Gate spell, and it specifically takes you out of "this plane of existence" just long enough to avoid the attack.
I could see it as an edge case, but in my games that "edge case" goes in favor of magic. You're not on this world but protected by magic but not in this world long enough to avoid the attack. To me that's a big difference - much like Blink, which moves you elsewhere to avoid an attack, you simply are using magic to not be where the attack is, not using magic to let the attack pass through you by becoming insubtantial to metal. Steelwraith is an easier, but also more limited, spell, than the prereqs for Phase (Magery 3 instead of 2, Plane Shift or Ethereal Body). Heck, Ethereal Body takes you to a Low Mana Zone plane; it's clearly "not here" and not just "no clipping" and yes, you can use it to pass meteoric iron (but not some other substances in my game, but that's another topic.)
So doesn't Iron Arm work? You're still there to suck up the hit, you're just making your arm as hard as iron to suck the blow up harmlessly. That to me seems like it falls on the meteoric's side of the table, and you should get cut - it's too close to "affects the weapon."
Deflect is an odd case in my games. For one, I do not allow Deflect on armor, only on shields. Why? Because then people buy Deflect piecemeal, and I need to know the exact hit location before I know if an attack hit because it matters for their defenses. That annoys me, so I just said no this campaign.
I do allow it on shields, and I have rules that the DB bonus from Deflect, like the DB bonus from Shield, is ignored by meteoric weapons. That little magical extension that makes the shield act as if it was bigger doesn't stop the meteoric weapon.
Fortify, however, doesn't get ignored. Deciding to make NMZs a lot less annoying from an "what's my encumbrance now?" perspective, I ruled that, sort of like in the Morlock Ambrosius books, spells like Fortify re-arrange the structure of the substance it is cast on. Lighten removes some of the actual material weight, too, and that weight won't come back just because mana isn't there** So similarly, they help against meteoric weaponry.
The Armor spell doesn't, because it's a forcefield, not an enchancement to a piece of material.
Similarly, offensive/utility spells follow the same type of rules. You can't cast Apportation on a meteoric weapon, but you can Levitate its wielder (he's carrying it, not you.) You can't Lockmaster a lock with a meteoric pin built into the lock, but your magically-created golem or summoned demon can kick the door down (and so could your Barbarian friend you just hit up with Might.) You can Great Haste a meteoric sword wielder, but not cast Flaming Weapon on his sword. Your Windstorm spell will mess with meteoric arrows easily - the wind is magically generated, but it's still real wind. You can't Shape Metal the sword but you can Shape Metal into a shield and block it.
And of course, meteoric ignores magic, not sanctity. And in my games the gods ignore the rules of mana. So the Holy version of any of those spells works normally! Missile Shield by the Artificer-Priest will nudge your silly magically-dead arrow aside and the party cleric can put Flaming Weapon on it.
The theme here is:
Affects the weapon directly? Doesn't work.
Uses magic to stop the weapon's effects? Doesn't work.
Uses magic indirectly to avoid the weapon or otherwise stop it? Works.
Is triggered by contact with an item? Generally doesn't work (meteoric swords are great for stabbing people with Flaming Armor.)
Is it not magic? Then it works.
In my experience, this seems like you get some surface incongruity ("I can't Steelwraith it but you can Phase away? This game sucks.") But in practice, it lets me rule on everything without creating inconsistencies or further edge cases. It's generally very clear which way it should go.
And that's how I do it.
* And I mean entirely meteoric iron arrows. Kromm has said that meteoric doesn't create a "wake effect" to get through defenses, so the entire item needs to be meteoric iron - that's why it says "any metal weapon" and not "any weapon that includes metal." If you want stats for a solid iron arrow, Doug "Gaming Ballistic" Cole has you covered.
** They still detect as magical, and dis-enchanting them can undo these effects - Remove Enchantment is pretty powerful. But they're permanent in a non-Mana dependent way. Convenience trumps all - just say the laws of the universe work in ways that seem illogical to the human mind and be happy you didn't jump up from just under Heavy to just over Heavy because of that NMZ.