Fireballs vs. Defended Locations

[ptolemy18]

Hello everyone,

I have a question about Fireballs and other spells which have a "burst" effect and don't require ranged touch attacks. When & how does Cover come into play regarding them?

Specifically... say that there is a fortified tower where the only openings are arrow slits. If someone is shooting arrows at the people behind the arrow slits, then obviously the people behind the arrow slits get a Cover bonus to AC.

But if a wizard casts a fireball at the people inside the tower, intending for the fireball to go off inside the tower, do the people get Cover bonuses to their Reflex Saves? Since a fireball doesn't require a ranged touch attack, it seems that the wizard doesn't need to make a roll to slip the fireball through even the tiniest opening (such as an arrow slit). And once inside, the fireball can explode centered on a square within the tower, so the people in the tower wouldn't get any Cover bonuses. (Like tossing a grenade through an elevator door just before it closes.)

However, this seems kind of exploitable and unfair. Am I misinterpreting it? Would the people inside the tower get Cover bonuses relative to the spellcaster's ability to see them, even though they wouldn't actually have cover relative to the outward-expanding fireball itself? Or do fireballs indeed just kick that much ass, and the only way to defend against them is to have a completely-sealed-up building with not even the smallest opening?

Jason

 

[fafhrd]

You get the cover bonuses when the cover is interposed between yourself and the source of the effect. Read the full description on fireball. It specifically mentions that if you target the spell through a sufficiently small space, you need to make an attack roll.

 

[Jack Simth]

Fireball

Evocation [Fire]
Level: Sor/Wiz 3 Components: V, S, M Casting Time: 1 standard action Range: Long (400 ft. + 40 ft./level) Area: 20-ft.-radius spread Duration: InstantaneousSaving Throw: Reflex half Spell Resistance: Yes

A fireball spell is an explosion of flame that detonates with a low roar and deals 1d6 points of fire damage per caster level (maximum 10d6) to every creature within the area. Unattended objects also take this damage. The explosion creates almost no pressure.

You point your finger and determine the range (distance and height) at which the fireball is to burst. A glowing, pea-sized bead streaks from the pointing digit and, unless it impacts upon a material body or solid barrier prior to attaining the prescribed range, blossoms into the fireball at that point. (An early impact results in an early detonation.) If you attempt to send the bead through a narrow passage, such as through an arrow slit, you must “hit” the opening with a ranged touch attack, or else the bead strikes the barrier and detonates prematurely.

The fireball sets fire to combustibles and damages objects in the area. It can melt metals with low melting points, such as lead, gold, copper, silver, and bronze. If the damage caused to an interposing barrier shatters or breaks through it, the fireball may continue beyond the barrier if the area permits; otherwise it stops at the barrier just as any other spell effect does.

Material Component: A tiny ball of bat guano and sulfur.

(Emphasis Added)

So there is a touch attack involved for that circumstance... but not against the AC of those inside.

Fireball is a bit of an exception, though; depending on the size of the arrow slits, almost no other spells will get through due to line of effect rules:

Line of Effect: A line of effect is a straight, unblocked path that indicates what a spell can affect. A line of effect is canceled by a solid barrier. It’s like line of sight for ranged weapons, except that it’s not blocked by fog, darkness, and other factors that limit normal sight.

You must have a clear line of effect to any target that you cast a spell on or to any space in which you wish to create an effect. You must have a clear line of effect to the point of origin of any spell you cast. A burst, cone, cylinder, or emanation spell affects only an area, creatures, or objects to which it has line of effect from its origin (a spherical burst’s center point, a cone-shaped burst’s starting point, a cylinder’s circle, or an emanation’s point of origin).

An otherwise solid barrier with a hole of at least 1 square foot through it does not block a spell’s line of effect. Such an opening means that the 5-foot length of wall containing the hole is no longer considered a barrier for purposes of a spell’s line of effect.

(again, Emphasis added).

Two foot high arrow slits that are only three inches wide don't qualify, so long as they are spaced at least 5 feet apart. For the most part, you can't cast at defenders inside a well-designed fortress without first demolishing the fortress. Fireball would seem to get around that limitation.....

 

[Hammerhead]

Two foot high arrow slits that are only three inches wide don't qualify, so long as they are spaced at least 5 feet apart. For the most part, you can't cast at defenders inside a well-designed fortress without first demolishing the fortress. Fireball would seem to get around that limitation.....

Most of the arrow "slits" that I've seen are much wider than three inches apart.

 

[Plane Sailing]

I have a question about Fireballs and other spells which have a "burst" effect and don't require ranged touch attacks. When & how does Cover come into play regarding them?

It is worth pointing out that fireball isn't a burst, it is a spread. That means that fireball tends to ignore most cover because it just spreads around the corners.

Cheers

 

[nittanytbone]

Obviously all well designed fantasy fortresses are subdivided into rooms with heavy oaken doors to be closed in case of a fight, just as modern navy ships use bulkheads and seperate compartments to mitigate any leaks or battle damage

 

[nittanytbone]

Ooh, or if you're really willing to spend a lot for a top-notch fortress, you could pay for Open/Close cantrips to be put onto all your doors linked to some sort of magical trigger. That way, when the Castellan declares "red alert" all the doors can slam shut, thus compartmenting the fortress and preventing any one fireball from toasting more than about half a dozen archers at once!

 

[Jack Simth]

Most of the arrow "slits" that I've seen are much wider than three inches apart.

Yes; but then, real castle builders didn't have to deal with someone deciding that nice long wall won't be an obstacle to casting a Wall of Fire just inside to burn out the entire force manning that wall...

 

[Elder-Basilisk]

Most of the arrow "slits" that I've seen are much wider than three inches apart.

You know, I thought that too when this came up on a yahoo group I posted to several years ago. But it turns out that in order for arrow slits to be big enough to cast spells though, they need to be 4 feet tall by 3 inches wide, 2 feet tall by 6 inches wide, or larger. (A cross-shaped arrow slit (most useful for crossbows I imagine) that was a two foot horizontal and a two foot vertical slit with a three inch width each way would still not be big enough for line of effect because of the nine square inch overlap in the middle.

When I did a web search and looked through my pictures of European fortresses, my information seemed to indicate that the 3 inch by four feet or 2 feet by six inches arrow slits were right at the top of the range for historical arrow slit size. Given the advantage that a D&D fortress builder could obtain by simply using the center and lower part historical arrow slit range, I imagine that the only ones big enough for line of effect would be specifically built for casters to cast out of (and would probably have some kind of shutter so that it could be opened to gain line of effect and then closed to deny line of effect to enemies in the same round (after casting some kind of a devastating spell out of it of course)).

 

[Nail]

In a past game, the PCs went up against a goblin fortress. The goblins were in groups of threes. Goblins #2 and #3 readied actions.

• Goblin #1 openned the shutter on the arrow slit.
• Goblin #2 had a readied action to fire as soon as the arrow slit was open.
• Goblin #3 had a readied action to close the shutter on the arrow slit once goblin #2 had fired.

What line of effect?

You just need to play by the rules of the system, man.