Cannons and magic!

[Shadowbane13]

i got a campaign going right now that, as most, have ships (both sea and sky). Now i put cannons into the game and as the DMG says, they can either be powered by arcana or explosives, up to the DM. In mine they are arcana. One of my players was wondering if dispel magic would work on a cannon because it is arcana. I know this is probably an "up to dm" thing but i wanted to see others opinions. Should dispel disable a cannon? If so, how long or does it permanently take it out?

[LibraryOgre]

Not only up to the DM, but also somewhat up to the system... I could see the answer being different in AD&D v. 4e, certainly.

My inclination? Dispel magic on a magic item like an arcana-powered cannon is only going to be short-term effective. Now, if the cannon itself is relatively non-magical, but the powder is magical, I could see a dispel magic spoiling a certain amount of powder. And, of course, there's always "slaver powder" from Guardians of the Flame.

Spoiler: Spoilers for an old series

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So, the MCs of the Guardians of the Flame are a group of college students stuck in their !D&D game. One of them was an engineer back in the "Other Side", and they all get into violent abolition, so he starts making gunpowder and firearms. The Slavers guild, allied with the Wizards Guild, wants to respond, but doesn't know how to make gunpowder. So, they take an iron sphere, put water in it, and then heat it past the point of plasma (yay, magic!). The result is a powder that, when you expose it to water, explodes. So slaver guns squirt water onto slaver powder, and explode the powder, which drives the bullet.

Major events in the story involve a wizard causing a bit of rain, and a man with a waterskin and a reckless disregard for his own life. (RIP Chak)

[Zarrgon]

A magic cannon is a magic item and can be effected by dispel magical normally.

[ExLibrisMortis]

A magic cannon is a magic item and can be effected by dispel magical normally.

That is to say, it'll be suppressed for 1d4 rounds, and then function normally.

1d4 rounds of suppression is a really bad deal if your cannon can only fire every minute or so anyway. So you might want to make an additional rule for cannon specifically, for example: "Loading a cannon takes 1 minute. If the cannon is dispelled while you're loading it, you'll have to start over once it becomes magical again". That way, you're at least getting about a minute out of one dispel (average ~7.5 rounds I think), instead of no effect at all.

[Lvl 2 Expert]

It could help to indeed define where the magic comes from. Is the cannon merely a sort of spell focus for a caster using them? Is it a magic device that can be used by say spellcasters and use magic device like a wand? Is the cannon magical in its own right and useable by anyone? Or is the powder magical? Define that and the solution will probably come to you.

[MoiMagnus]

For most intends and purposes, a canon is just a big magical ranged weapon, possibly using magic ammunitions too.
So the answer is the same as for dispelling the magic of a magic bow and magic arrows.
(ie it depends on usual rules about dispelling magic items)

[Quertus]

Or you could make the cannon a permanent Animated Object, and the cannon ball a returning orcish shotput. Dispel Magic on the cannon does nothing; on the cannon ball, however, it forces the cannon to stop "sneezing", and engage in melee for 1d4 rounds (or longer, if the cannon ball was hit in flight / fired while disenchanted, and doesn't simply return once its magic comes back online).

[Psyren]

In 3.5/PF, magic items can generally be affected by a targeted dispel - but (a) this requires a dispel check which may fail, and (b) even if it succeeds, will only suppress the magical properties of the item for a short amount of time (usually 1d4 rounds, i.e. less than 30 seconds maximum.) Depending on how exactly the cannon works, it may be usable as a normal cannon in the interim, or it may not.

[Clistenes]

I suggest to combine a Decanter of Endless Water with Wands of Heat Metal to produce a steam-powered cannon...

[Altheus]

If cannons are powered with magical explosives then the spells "Detect Cannon" and "Detonate powder" will be swiftly developed.

[Lvl 2 Expert]

If cannons are powered with magical explosives then the spells "Detect Cannon" and "Detonate powder" will be swiftly developed.

Talk about scry and die.

[Lord Torath]

In Spelljammer, the cannons are mundane, but use magical Smoke Powder as a propellant. The primitive firearms in the game (arquebus, flint lock, wheel lock) use the same power, just in smaller amounts.

[Anymage]

Which edition? 5e Dispel Magic only affects spell effects and says nothing about magic items.

And yeah, ultimately up to the dm how much magic is involved. Assuming you're playing an edition where Dispel does affect magic items, there's a difference between a world where the whole thing is a magic item, vs. one where you stick a nonmagical metal ball into a nonmagical metal tube and then rely on magical smokepowder as the propellant.