Magnificent Mansion on a ship?

[Tyger]

If one casts MMM (D&D 3.5) while on board a ship at sea, does the portal remain anchored to the boat, or would it hover in space if the boat moved?

What if the boat sank?

[Clistenes]

I don't think the rules say anything about that, so it could go both ways. I personally think the portal would hover in space, but it should be easy for a mage to research a version of the spells that anchors the portal to a physical door frame, or to another physical feature, like the board of a ship. If you chose Magnificent Mansion as one of the spells you gained through personal research instead of copying it, you should be able to decide those little details.

[Cirrylius]

Relative reference frames are tricksy in D&D. Wall of Force cast on a ship could make an awesome bit of cover, or it could shear off all the masts and scrape everyone on deck into the water.

[Emperor Tippy]

Ask your DM. The problem is that it is not specified what spells are stationary in regards to. And pretty much whatever the frame of reference for the spell is, there is something highly powerful that it makes possible.

[Mnemnosyne]

I would personally rule that it's up to the caster as to what the frame of reference for the spell to be stationary in regards to is, but it has to meet some minimum size and/or weight so that you can't just make it stationary relative to something you can easily carry on your person.

[Emperor Tippy]

I would personally rule that it's up to the caster as to what the frame of reference for the spell to be stationary in regards to is, but it has to meet some minimum size and/or weight so that you can't just make it stationary relative to something you can easily carry on your person.

Muhahaha. I cast Wall of Force stationary relative to the sun, while under ground. I just tore a good chunk out of the planet.

Or stationary in regards to the moon.

[Mnemnosyne]

Haha. Good point...limit on how far away the object it's stationary in reference to can be seems like the best answer to that, so it can't be made stationary relative to a distant astronomical body.

Although thinking about it, even this causes some issues. Wall of force on an ship, relative to the ship. If the wall can be dragged without exerting resistance on the ship, then you can maneuver in such a way as to plow the wall through solid rocks and other such things. On the other hand, if it exerts resistance on the ship, then you can cast it on an enemy's ship, underwater, and assuming it counts as an unattended object, the ship would need to displace all the water that the wall of force would move in order to move. It'd be yanked to a sudden dead stop.

[zlefin]

switching to PF walls of force which aren't invulnerable would help with that. they may have high hardness and hp, but the amount of damage that should be involved with ramming solid rock could cause it to dissipate fairly readily.
Also i'd say at a minimum, the frame of reference has to be something within the cast range.

[Jack_Simth]

Muhahaha. I cast Wall of Force stationary relative to the sun, while under ground. I just tore a good chunk out of the planet.

Or stationary in regards to the moon.

Let's see... can we make it less abusable?

The thing it's stationary in relation to must meet all of the following criteria:
1) The thing it is stationary in relation to must be within range of the spell.
2) The thing it is stationary in relation to must be solid (so no anchoring it to a wind or a current).
3) The thing it is stationary in relation to must be at least one order of magnitude larger in size than the effect of the spell in every dimension.

So: What abuses would still be possible with, say, Wall of Force if we add those?

[Deophaun]

In general, I say it's relative to the strongest gravity well unless anchored to something solid. If you put a wall of force on a boat, it's relative to the boat. If you put it in air in front of the boat, then it's relative to the planet and the ship is going to hit it. If you are out in space with nothing terribly close by and you cast Wall of Force, then it can be relative to you.

[Jack_Simth]

In general, I say it's relative to the strongest gravity well unless anchored to something solid. If you put a wall of force on a boat, it's relative to the boat. If you put it in air in front of the boat, then it's relative to the planet and the ship is going to hit it.
Which is still very useful, as it means you've got a pretty effective way of killing a boat.

[Alleran]

FWIW, although I know it's Pathfinder rather than standard 3.5e, the Skull & Shackles Player's Guide (and the d20pfsrd write-up of the Magnificent Mansion spell) specifies that the entrance created by the spell does not move with a ship.

However, I don't think there's anything else that says so one way or the other.

[Nymrod]

I personally make it so all such things have to be stationary to the ground at the location of the caster when he casts the spell. It's a houserule.

[Fouredged Sword]

I would rule, in one of my games, that the spellcaster has two choices when casting a spell. He can ether anchor the spell to the worlds frame of reference, OR he could anchor it to the surface of the square it is cast on, but only if the square is large enough to fill at least a significant portion of the effect and stable enough to count as a surface on the battle map.

I know it isn't the solidest of rulings, but I feel that this would make for the easiest to understand play and most fun.

[Eldan]

Let's see... can we make it less abusable?

The thing it's stationary in relation to must meet all of the following criteria:
1) The thing it is stationary in relation to must be within range of the spell.
2) The thing it is stationary in relation to must be solid (so no anchoring it to a wind or a current).
3) The thing it is stationary in relation to must be at least one order of magnitude larger in size than the effect of the spell in every dimension.

So: What abuses would still be possible with, say, Wall of Force if we add those?

Hm. Really small wall of force, anchored to a catapult stone, but about sixty feet lower. Shoot it in the air over the enemy fortifications, watch as the wall plows a hole through anything.

[Carth]

For what it's worth, Stormwrack has Mordenkainen's capable caravel, which creates a boat with a mage's mansion that explicitly does move with the boat, and it lasts for 1 day per two CL.

[DigoDragon]

In my games, I rule things like MMM and Wall of Force to be anchored to the ("relatively" horizontal) ground it's cast upon (I treat MMM's portal like a door for purposes of what it can rest upon). So if cast on a ship's deck, MMM should remain anchored to the ship.

If the ship sinks... well you get a high-pressure salty shower in the morning. :smalltongue:

Other people may rule it differently, but this works for my players.