How would you dig through stone to build a cave? [closed]

Question

We're playing Waterdeep: Dragon Heist and we

just got our mansion.

I play a gnomish Artificer/Wizard and want to build my workshop

in the mansion's basement. But it's quite small for what I have in mind. Digging seems not to be a viable option to expand the basement, because the ground is pretty hard.

What kind of spell, non-magic or half-magic solution (ie. machines) could do the trick? I come from 3.5e. Back then there were several midlevel options to do that. Stone to mud + Mold Earth. But there is no Stone to mud, or I am not finding it.

Maybe here's someone who had the same idea and made it work or you just know a way to make it work. I'm very curious about how you achieved this.

FYI Our DM is pretty liberal and let's us do pretty much, so feel free to stretch the rules. I don't talk about home-brew, but RAW is not that important with this one: RAW answers are preferred though.

Some Details

The basement is carved into stone and around 6 by 4 squares big and around 10ft high. I'm thinking of doubling it in size... ie 6 by 8 squares. There are no special constraints besides the stone, which is (according to my DM) "not as hard as granite but still pretty hard". We're playing Dragon Heist very loosely interconnected and can do with our time, whatever we want. The whole campaign is about one year long in-game, so to use that space the time frame should be around one or two months. So I'm not necessarily looking for a quick solution.

Constraints

During this campaign, we will end up with level 8-9 (according to my DM). I plan to have 2 levels of wizard and the rest in artificer. 3rd level spells is the maximum level that I will be able to cast during this campaign.
Right now, I'm broke, but I'm pretty sure that it'll change in the near future. This goal is more of a long term thing anyway as I already mentioned.

I ask for general possibilities besides the obvious: Just dig, Dude! At least if it's not the only possibility. If plain digging is the only way, it's the only way and I have to dig or let someone else do the digging. Feel free to list all the possibilities that there are in the game or mention some examples out of experience when you tried to accomplish a comparable task.

Answer 1

Hire a bunch of labourers

Get a team of people with pickaxes and baskets.

Waterdeep is a big city. Labourers will be easy to find.

Answer 2

Transmute Rock

This is 5e's Stone to Mud spell (and it also does Mud to Stone). You can find it in the Elemental Evil Player's Companion, page 22 or Xanathar's Guide to Everything, page 169.

It's a 5th level spell, and it's available to wizards. It can transmute up to a 40 ft cube of stone into mud (that's 8 squares a side; more than sufficient for your needs). And it makes the change permanently, giving you as long as you like to then remove the mud from your basement.

Answer 3

Stone Shape? can do this

That is literally Mold earth but for stone, as requested. Available for Cleric, Druid and Wizard, so it perfectly fits. Your problem (now that you edited the question) is that you need scrolls to do this, and will need to made a DC 14 check to cast said scrolls. That could get expensive.

I'm not absolutely certain whether this can remove stone, but even if it can't, just reshape it into separate bricks that anyone can easily carry away. The spell only limits your mechanical detail, something that absolutely won't be a problem. It will take a number of casts, but the volume is actually quite decent at 5x5x5 feet for a lvl 4 spell slot.

If you have access to Disintegrate (a favor from someone you meet in Waterdeep) that's a somewhat quicker way, or both combined, since you cannot upcast Stone Shape.

Answer 4

Firebolt or Magic Stone, over and over again.

Firebolt and Magic Stone are damaging cantrips that can target objects. Firebolt can do so explicitly, Magic Stone can do so implicitly by not limiting its targets to creatures.

Firebolt:

You hurl a mote of fire at a creature or object within range. Make a ranged spell attack against the target. On a hit, the target takes 1d10 fire damage. A flammable object hit by this spell ignites if it isn't being worn or carried.

Magic Stone:

You touch one to three pebbles and imbue them with magic. You or someone else can make a ranged spell attack with one of the pebbles by throwing it or hurling it with a sling. ... On a hit, the target takes bludgeoning damage equal to 1d6 + your spellcasting ability modifier.

Stone isn't flammable, so the last sentence of Firebolt isn't triggered; on a hit, it will just take damage. A 10x10 segment of stone would be a Large object, with 17 AC and 5d10 (27) HP, according to the DMG's section on object statistics (pp. 246-247).

That section does mention the possibility of Damage Thresholds for items like 10x10 sections of castle wall, but it gives no guidance about what those Damage Thresholds should be, effectively making Damage Threshold an avenue for a GM to declare via GM fiat that a given attack doesn't work. Thus, for this answer, I'm disregarding Damage Threshold, but your GM might rule that this strategy doesn't work, citing the Damage Threshold "rule".

So, a level 1 Wizard or Artificer with 16 Int could expect to spend just over a minute blasting a section of stone over and over again with Firebolt or Magic Stone in order to carve a 10x10 tunnel through the rock.