How Exactly Does Obsidian Flow (spell) Work?


Rules Questions


Spell in question.

Details:

Casting
Casting Time 1 standard action
Components V, S, M/DF (a small piece of obsidian)
Effect
Range close (25 ft. + 5 ft./2 levels)
Area 20-ft.-radius burst
Duration instantaneous
Saving Throw Reflex partial, see text; Spell Resistance no
Description
You convert a thin layer of the ground to molten glass that cools quickly. Creatures in the area take 1d6 points of fire damage per two caster levels (maximum of 10d6) and become entangled. Any creature within the area that makes a successful Reflex save takes half damage and is not entangled. An entangled creature can attempt to free itself by spending a move action to attempt a Strength check or Escape Artist check (the DC equals the spell’s saving throw DC).

The ground is covered with slippery expanses and sharp shards of obsidian. The area of effect is difficult terrain, and the DC of Acrobatics checks within the area of effect increases by 5. A successful DC 15 Acrobatics check is required to run or charge across the area. A creature that falls prone in the area takes 1d6 points of damage from sharp obsidian.

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For reference, the Entangle spell:

Casting Time 1 standard action
Components V, S, DF

EFFECT

Range long (400 ft. + 40 ft./level)
Area plants in a 40-ft.-radius spread
Duration 1 min./level (D)
Saving Throw Reflex partial; see text; Spell Resistance no

DESCRIPTION

This spell causes tall grass, weeds, and other plants to wrap around creatures in the area of effect or those that enter the area. Creatures that fail their save gain the entangled condition. Creatures that make their save can move as normal, but those that remain in the area must save again at the end of your turn. Creatures that move into the area must save immediately. Those that fail must end their movement and gain the entangled condition. Entangled creatures can attempt to break free as a move action, making a Strength or Escape Artist check. The DC for this check is equal to the DC of the spell. The entire area of effect is considered difficult terrain while the effect lasts.

If the plants in the area are covered in thorns, those in the area take 1 point of damage each time they fail a save against the entangle or fail a check made to break free. Other effects, depending on the local plants, might be possible at GM discretion.

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For example, there's a level 12 Arcanist in the group with 26 Int. If he casts this spell and uses Potent Magic, enemies have to make a DC 10 + 4 + 8 + 2 = 24 Reflex Saving throw.

If they fail, they're rooted in place literally forever unless they make a DC 24 Strength check (so anyone with 18 Strength or less literally has to roll a natural 20) or make an Escape Artist check (so someone with that skill could get out fairly easily).

Is that correct?


Balkoth wrote:
If they fail, they're rooted in place literally forever ...

Yes. Until they get free. Despite it not being listed, I would also allow damaging and breaking the obsidian as an option. Obsidian is basically glass, so with some work at smashing or chipping it away, or suitably powerful hit, I would allow someone to break free. That would use up a creature's standard action, rather than the move action required to break free or escape normally needed.

Also, if you or your GM consider obsidian to be both a volcanic glass (which it is) and a stone (being an igneous rock), then effects like stone shape or certain solvents or acids could also be used.


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An additional, small correction: natural 20s are not automatic successes on ability or skill checks, so those with insufficient strength or escape artist bonuses cannot hope for a 20 to save them.


Another thing to note is that it's a level 4 spell, as opposed to entangle, which is level 1.


Pizza Lord wrote:
Also, if you or your GM consider obsidian to be both a volcanic glass (which it is) and a stone (being an igneous rock), then effects like stone shape or certain solvents or acids could also be used.

I am the GM. I've limited the books severely and have most things per approval only, a player asked me about this spell.

If I allowed it, how would you adjudicate breaking free?

Java Man wrote:
An additional, small correction: natural 20s are not automatic successes on ability or skill checks, so those with insufficient strength or escape artist bonuses cannot hope for a 20 to save them.

True, so someone with 16 or less strength who also lacks Escape Artist could apparently never get free.

willuwontu wrote:
Another thing to note is that it's a level 4 spell, as opposed to entangle, which is level 1.

Yeah, except that puts it on the scale of Greater Magic Weapon or Ice Storm.

Frankly it seems like Entangle was assumed to only be used at low levels where the maximum DC would be like 15ish, so even someone with a -1 to Strength had a 25% chance to break free.


Balkoth wrote:
Pizza Lord wrote:
Also, if you or your GM consider obsidian to be both a volcanic glass (which it is) and a stone (being an igneous rock), then effects like stone shape or certain solvents or acids could also be used.
If I allowed it, how would you adjudicate breaking free?

It's only described as a thin layer, so I wouldn't assume more than an inch or so of thickness. Obsidian items typically have half the hardness of a normal item but no noted change in hit points. If you consider it stone in this case (glass would probably be a little more fragile than I imagine), it would be hardness 4 with 15 hit points. So an acid (that affected glass and stone, which most may not if stored in glass vials) would have to do that much.

For stone shape, it should just work.

Quote:
True, so someone with 16 or less strength who also lacks Escape Artist could apparently never get free.

Yes, though the example DC is pretty high for a normal situation. If they had to, they could spend 2 minutes Taking 20 (which would still fail) but an ally could Aid Another or there could be another tool or material they could use for a bonus (not sure I'd allow a crowbar, but a tool similar to that, which wouldn't just be breaking the obsidian, like an oil or something).

Since it's described as hardening, like a cast or mold, unlike web or entangle which are considered constantly resticking or trying to hold the target, you might allow a creature reduced or changed to a smaller size to receive a bonus (they usually increase Dex as well when that happens).

Otherwise, a grease spell on their boots should suffice with its +10 circumstance bonus to Escape Artist. They might want to dispel it before walking around afterwards. (Technically greased armor allows such a bonus, but the spell description is such that it seems to be around your feet, so a fair GM call is that your greased breastplate doesn't help, unless maybe you were prone when it happened.)


A Wizard(Conjuration) at 8th level gets Dimensional Steps (Sp). This can get out.
The Travel Domain gets Agile Feet (Su). This can get out.
The Gaseous Form spell will work.
Alter Self should let a medium creature become small, which could get them out.
The Ring of Seven Lovely Colors will work.

As for Aid Another, you should be able to get 8 creatures around the trapped one to aid. Guidance would add +1 as well.

/cevah


Really the spell should just provide some rules for breaking the obsidian (glass) for a creature to free themselves. I'm thinking hardness 1 with hp equal to caster level.


Claxon wrote:
Really the spell should just provide some rules for breaking the obsidian (glass) for a creature to free themselves. I'm thinking hardness 1 with hp equal to caster level.

Obsidian's structure makes it as tough as normal stone. Once upon a time I had a job for a couple of months preparing rock samples, I have experience of this. RAW obsidian weapons have the same hardness as stone weapons (5).


Claxon wrote:
Really the spell should just provide some rules for breaking the obsidian (glass) for a creature to free themselves. I'm thinking hardness 1 with hp equal to caster level.

It does. An entangled creature can attempt to free itself by spending a move action to attempt a Strength check or Escape Artist check (the DC equals the spell’s saving throw DC).

What do you think you're doing with a strength check here? Impressing the obsidian with some mighty flexing? Cowing it into submission by only making one trip from the car to the house with the groceries?


Making a strength check and hitting it with a weapon are two very different things.

Strength check it more like "kicking through" the obsidian that your feet are encased it.

Attacking it with a pickaxe is more like mining.

At AVR, Obsidian fractures pretty easily though. You're not trying to pulverize it, you're just trying to break it enough to get your feet lose.

Though honestly I don't care if its hardness 1 or 5.


How about the DC drops by the damage done.

/cevah


avr wrote:
Claxon wrote:
Really the spell should just provide some rules for breaking the obsidian (glass) for a creature to free themselves. I'm thinking hardness 1 with hp equal to caster level.
Obsidian's structure makes it as tough as normal stone. Once upon a time I had a job for a couple of months preparing rock samples, I have experience of this. RAW obsidian weapons have the same hardness as stone weapons (5).

Interesting. Your average person with a dagger could never free themselves in this case. Someone armed with a short sword would have to hack at it for an average of 9 minutes (1/6 chance of rolling a 6 on damage for 1 point, 15 points needed.)


Cevah wrote:

How about the DC drops by the damage done.

/cevah

The rules do support this (somewhat). When an object is dropped to half hit points (typically when it gains the broken condition, though I don't necessarily consider this an object), the DC to break it with a Strength check drops by 2.

As we've all noted, however, there's no in-spell reference to hardness/hit points unless we're to assume that the correlation between the spells effect and stone were so obvious as to be unnecessary in the writer's/editor's eyes.


Ultrace wrote:
avr wrote:
Claxon wrote:
Really the spell should just provide some rules for breaking the obsidian (glass) for a creature to free themselves. I'm thinking hardness 1 with hp equal to caster level.
Obsidian's structure makes it as tough as normal stone. Once upon a time I had a job for a couple of months preparing rock samples, I have experience of this. RAW obsidian weapons have the same hardness as stone weapons (5).
Interesting. Your average person with a dagger could never free themselves in this case. Someone armed with a short sword would have to hack at it for an average of 9 minutes (1/6 chance of rolling a 6 on damage for 1 point, 15 points needed.)

*Considers large kitchen knives vs. stone* Sounds about right.

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