Volcano stats?

So, I’m working on a new home brew campaign. It’s relatively lose and I already told my players it’s more of a side project.
The idea I have in mind is to use a volcano very early on in the campaign, which goes off suddenly and basically destroys the center of the continent, and as the players help around and look more into it they find out it’s not by natural cause, but by a powerful Balor, using a magical item to make a rip between this plane and the fire plane to cause destruction.
The thing is that I’m not sure how to work with it. The volcano is definitely something that remains a problem, possibly for the entire campaign. But how fast does it go? What kind of destruction does it leave? And for the Balor: what kind of magic item (possibly corrupt artifact) could he have that causes such destruction?
Theres a lot of questions, and there’s a large chance I’ll be winging most of it. But it’s nice to have at least some basic stats down.

These sound exactly like the kind of story points that I'd handwave. Ask yourself, do you really need stats here? How do the players mechanically engage with the volcano? Is it meaningful? I recommend instead of worrying about stats, take that time and spend it on lore. Who is the Balor? Why is it here? What is its agenda? What is this artifact? Who knows about it? Who wants it? How can it be destroyed? Etc.

Good point. It was more or less so I can keep an eye on how bad the damage becomes after a certain amount of time, and when the damage starts to become less. But I suppose that’s easy enough to just squint an eye at. Thank you!

I'll start. Feel free to add.



Volcano
____________________

Movement: 0

Volcanoes delve into the realm of "Plot damage"

But for the sake of playability, you have three things to worry about:

Lava. It flows up to 40 MPH, which is approximately 70 squares per turn. And it would ignite any flammable material in the surrounding area. For comparison, a rogue double-dashing can move 18 squares. Thus I highly recommend making it move somewhat slower for any encounter that is centered around it.(after all, it has to make a channel first)

Ash. It will be spewing this stuff out, covering an area of hundreds if not thousands of square miles (easily the entire continent depending on prevailing winds) The Ash itself is hot for a while after leaving the volcano, but it's most important effects are obscuring vision (because it blots out the sun) and making it hard to breathe in general. The long-term fallout of cooling off the area is something to be dealt with in the aftermath of the campaign, if ever.

Boulders. The initial eruption, and aftershocks triggered by the Balor, would spew rocks everywhere. For an example:

Data from a very extensive study of the AD 79 Vesuvius eruption by Haroldur Sigurdsson shows that for each of two particularly strong blasts during the eruption, the pumice layer was 100 cm thick up to ~20 km downwind, 50 cm thick out to about 50 km, 25 cm thick out at ~60 km, and so on. Pumice 15 cm in diameter made it out ~6 km downwind, 10-cm pumice made it ~7 km, and 5-cm pumice even further.

Click to expand...

That means the surrounding area is going to be buried in rocks. Something like death from a million sling bullets. But for dramatic effect, and to hint that something is actually controlling this disaster, you could have targeted giant flaming boulders fall on key areas. Note that this will be a very obvious attack with a long travel time, so feel free to have it deal lots of damage (in the scale of this will outright destroy a house or castle wall) and give the opportunity for the players to run away from it. Or maybe make it deal 8d10 damage(double against a structure) like a trebuchet if you absolutely need numbers.

That is some very useful information! I feel a lot more prepared reading that.
I’ve been looking into animations of what vulcanic explosions like Pompeii looked like (which is terrifying, ngl), and seeing how fast everything happens, I’m afraid that I’ll have a TPK on my hands. So I think it’s saved to just have signs of the volcano being active first (earthquakes, whitish-gray smoke) so they will have two or three days to evacuate together with the village and gain some distance.

Rather than stat out the volcano stat the balor. Make him a balor from the mm but with the volcano as a lair. Max out each hd for Maximum hitpoints.

Maybe alter his teleport skills and give him something else instead (Surfing on Lava ?)

Give him a lot of lair Actions and use these rather than going for a melee with the Group: e.g. ash rain, pyroclastic attacks, rifts in the ground minor earthquake (as the spell) etc.

The balor will not perceive the Group as a threat soon, since he is connected with the volcano he thinks he is invincible.

The artifact in question could be some big Magic ruby gem which could (unbenownst to the balor) double serve as some soulgem (of an elemental Lord? )
Its powers are above mentioned lair control plus artefact posession.

If you want to stat up a volcanic Balor, I'd suggest that you take a look at the statblock for Maegera the Dawn Titan. Its a literally a walking volcano. Just add some demonic features, like summon some demons instead of fire elementals, and you have a nice demonic walking volcano as end boss.

Coroc said:

Rather than stat out the volcano stat the balor. Make him a balor from the mm but with the volcano as a lair. Max out each hd for Maximum hitpoints.

Maybe alter his teleport skills and give him something else instead (Surfing on Lava ?)

Give him a lot of lair Actions and use these rather than going for a melee with the Group: e.g. ash rain, pyroclastic attacks, rifts in the ground minor earthquake (as the spell) etc.

The balor will not perceive the Group as a threat soon, since he is connected with the volcano he thinks he is invincible.

The artifact in question could be some big Magic ruby gem which could (unbenownst to the balor) double serve as some soulgem (of an elemental Lord? )
Its powers are above mentioned lair control plus artefact posession.

Click to expand...

My thoughts exactly - Balor with Lair Actions.

You could use spells like meteor swarm (lava bombs), earthquake (uhh, earthquakes), a fast-moving cloudkill (pyroclastic flow). Maybe the Balor can summon some fire elementals too.

One school of thought is, if someone touches lava, then that one dies, no save.



So, it is better to think in terms of an aura of fire damage.