Fireball targeting

[Old_school_overlord]

I've got a dungeon coming up that will include archers shooting from murder holes and arrow slits.

I'd anticipate the party's sorcerer will want to launch fireballs so the detonate inside the enemy defences, but there aren't really any rules i'm aware of to determine if this is anything other than an automatic success...

I'm leaning toward making it a touch attack against DC 18 (since they provide a +8 to ac) with a range increment of 20 ft. Any thoughts?

Similarly, any rules for throwing fireballs past the melee line for hitting the monsters only?

Thanks

 

[Kask]

Line of sight, line of effect rules.

 

[Nimloth]

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.

Yes, a ranged touch attack to hit the opening. Anyone know the ac of a arrow slit? I might base it on size, not how much ac it provides. But thats just my opinion, YMMV.

Throwing a fireball past a melee, I usually just allow it, but would not object to a reasonable "to hit" roll being required.

 

[Vegepygmy]

I'd anticipate the party's sorcerer will want to launch fireballs so the detonate inside the enemy defences, but there aren't really any rules i'm aware of to determine if this is anything other than an automatic success...

The fireball spell description says: "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."

I'm leaning toward making it a touch attack against DC 18 (since they provide a +8 to ac) with a range increment of 20 ft. Any thoughts?

Spells do not use range increments. If you have to make an attack roll with a fireball, you're either "in range" (no penalty) or not (just can't do it, period).

AC of an object (or opening) is 10 + its size modifier + its Dexterity modifier (usually -5). An inanimate object takes an additional -2 penalty to its AC. See "Smashing an Object," PHB page 165. See also Table 7-1 (Creature Sizes), MM page 314.

So a typical arrow slit (say 2-3 ft. high) is probably Small in size (+1 AC), maybe Tiny (+2 AC). Its touch AC will thus be about 4 or 5.

Similarly, any rules for throwing fireballs past the melee line for hitting the monsters only?

A fireball "hits" anything in its area of effect. If the caster chooses the right grid intersection (see "Aiming a Spell," PHB page 175), he'll "hit" the right targets. The melee line is irrelevant, since it does not block line of effect or create a sufficiently narrow gap to force an attack roll (see above).

 

[Old_school_overlord]

AC of an object (or opening) is 10 + its size modifier + its Dexterity modifier (usually -5). An inanimate object takes an additional -2 penalty to its AC. See "Smashing an Object," PHB page 165. See also Table 7-1 (Creature Sizes), MM page 314.

So a typical arrow slit (say 2-3 ft. high) is probably Small in size (+1 AC), maybe Tiny (+2 AC). Its touch AC will thus be about 4 or 5.

Good points on the object Rules Vegepygmy, but i don't think i can agree that an empty space can have a Dex, or be an inanimate object.

A 2 inch wide, foot long slot seems diminutive to me, so that would be 10+4 size = 14 AC touch attack.

 

[freyar]

Good points on the object Rules Vegepygmy, but i don't think i can agree that an empty space can have a Dex, or be an inanimate object.

A 2 inch wide, foot long slot seems diminutive to me, so that would be 10+4 size = 14 AC touch attack.

A slot can't move, so it should be inanimate, right? (We know it is an object because it has no Wis or Cha by RAW.) Furthermore, that means it has Dex 0 for a modifier of -5.

 

[Old_school_overlord]

A slot can't move, so it should be inanimate, right? (We know it is an object because it has no Wis or Cha by RAW.) Furthermore, that means it has Dex 0 for a modifier of -5.

Thats true, but considering the modest penalties for failure (ie. the spell still, goes off, just at the new location and the enemies receive a bonus to their save) I'm just not willing to let it be so easy its just a 2+ on the attack roll.

Thanks for the rules help though folks, guess i'm just gonna divert off them a bit on this one

 

[irdeggman]

Thats true, but considering the modest penalties for failure (ie. the spell still, goes off, just at the new location and the enemies receive a bonus to their save) I'm just not willing to let it be so easy its just a 2+ on the attack roll.

Thanks for the rules help though folks, guess i'm just gonna divert off them a bit on this one

Hmm the "penalty" is that the spell goes off in a different area but the enemeis have full cover for the effect.


The wall provides cover for that directin of the spread, if the spread can wrap around the corners of the wall it can affect the targets - but I'm guessing it can't wrap around in this case.

The effect does not pass through the wall.

 

[Nimloth]

If an arrow slit is only ac 4,5 or 14 to shoot through, how does it give someone behind it +8 to ac?

 

[freyar]

If an arrow slit is only ac 4,5 or 14 to shoot through, how does it give someone behind it +8 to ac?

The target can duck behind the wall part, so you have to aim cleverly through the slot, not just hit the slot.