# Creating a sink hole beneath a castle with Mold Earth and Portable Hole

This is a follow up to my related question on what materials can mold earth move.

Using a combination of Mold Earth (functioning as a shovel) and Portable Hole (as a bucket) "6 feet in diameter" ... "extradimensional hole 10 feet deep". Would it be possible to remove enough dirt under a castle (using the portable hole to move the dirt out) to achieve a sinkhole (possibly multiple trips)?

and while Mold Earth specifically says "This movement doesn’t have enough force to cause damage" ... could it be assumed that gravity might add damage to some of the residence of said castle in this case.

• – Arcemius Jan 25 at 3:15
• @CaffeineAddiction sidenote: the title was changed (not by me) not because people disagreed with your Minecraft reference, but because titles should describe the content of the question and "Dnd minecraft" didn't do that. – Rubiksmoose Jan 25 at 17:16
• I concur the title changes were an improvement as they more directly and clearly summarised the nature of the question. – doppelgreener Jan 25 at 17:33

Mold Earth allows you to remove "loose earth". The foundations of a castle (or any other structure) are not, in any way, "loose earth" as the weight of the building compacts granular material until the building stops sinking (or falls over).

A Portable Hole is structurally sound so putting one under a castle would still hold the castle up.

Sorry, you're going to have to use the tried and true method - picks, shovels and back-breaking labour.

• I think OP was planning to use the portable hole to carry dirt out and move earth to do the digging. His working off the current answer of the linked question. Crawford said move earth allows you to move "dirt not stone". – linksassin Jan 25 at 3:48
• I like the answer, but this belongs in rpg.stackexchange.com/questions/139836/… ... people get mad when I ask all the questions in 1 go ... so I split them up ... something about adding context to a question drives people on this SE bananas – CaffeineAddiction Jan 25 at 3:50
• @CaffeineAddiction actually we love context (usually the more the better), but we need questions to be focused on one issue at a time for the system to work. – Rubiksmoose Jan 25 at 5:17
• Stone to mud + Move Earth as a viable alternative? – Isaac Kotlicky Jan 25 at 8:39
• @Slagmoth At that point you're arguing semantics. All dirt contains some amount of moisture. – Isaac Kotlicky Jan 25 at 12:49

# Probably

Combat digging is called 'sapping' and is a part of actual real-life anti-castle warfare. Medieval sappers used a variety of tools to undermine fortifications, but moving loose earth was a significant part of the process. While mold earth is certainly not sufficient to undermine a fortification-- pickaxes and explosives being required for a lot of the work-- it should certainly help with a sapping effort.

Furthermore, besieging forces used saps extensively to mitigate defensive artillery and arrow fire while advancing their own siege weapons so as to deal more damage to the defending walls. These saps were not underground tunnels as with an undermining effort, but rather trenches and embankments such as one might picture on WWI battlefields, zig-zagging towards the fortification to attempt to avoid allowing the defenders to enfilade effectively. For this kind of sapping, mold earth is perfect; there's no need to mine through stone or hard-packed sediment.

Regardless of the strategy chosen, however, be aware that assaulting a castle is a dangerous business. Even with a carefully planned sap, fortification designs like the Italian Star Fort can ensure that defensive fire poses a real danger to would-be-besiegers, and undermining runs the danger of being ambushed by counter-miners.

Also, the portable hole is a waste of time and resources. There are far better uses in warfare for such a powerful artifact than to shovel dirt in a manner more efficiently done via Mold Earth itself or a line of untrained laborers or men of the line. Furthermore, you usually don't want to move the dirt very far unless you are undermining; embankments about your trench are an important part of granting yourself cover.

• A note, if you are digging a well you usually need a shovel and a bucket ... in the case above, the portable hole is my bucket (specifically to not waste time and resources in the effort to move the dirt larger distances than mold earth can). Good answer though, +1 – CaffeineAddiction Jan 26 at 6:07

No. Sink holes are created when running water removes earth beneath the surface. Eventually the surrounding dirt is unable to support the surface (the top of the open space) and the remaining ground collapses.

This effect could be created by something other than water (for example, sappers basically used this technique to bring down castle walls by tunneling under the walls then burning the tunnel supports), but the Mold Earth spell specifically states that the excavated earth moves "along the ground", which implies across the surface. So you could dig a hole if the ground was loose earth, but you could not remove earth below the surface and get a destructive sink hole effect.

•If you target an area of loose earth, you can instantaneously excavate it, move it along the ground, and deposit it up to 5 feetaway. This movement doesn’t have enough force to cause damage.

• No. Sink holes are created when running water removes earth beneath the surface. not always ... there are many cases where coal mining has lead to houses slowly sinking into the ground. – CaffeineAddiction Jan 25 at 16:19
• True - other things can cause sinkholes besides water, but the key is that the earth is removed below the surface. Mold Earth specifies that the loose earth is moved "along the ground" which implies on the surface. You could use the spell to create a hole, but not a SINKhole. – Pugmonkey Jan 25 at 19:33
• Thats an interesting detail to latch on to, lets debate that for a sec. If you have a cup of water and fill it to a brim, it could be said that the layer at the top is the waters surface. If you remove some and look back at the cup ... the water still has a surface just at a lower point. Further, if you put a lid on the cup ... the water still has a surface ... its just that that surface is lower than another surface. This argument could similarly be made replacing "surface" with "ground". By your logic, I wouldn't be able to make a pile of dirt either ... unless the surface could move. – CaffeineAddiction Jan 26 at 5:59

# Depends on your DM and the specific circumstances

If you target an area of loose earth, you can instantaneously excavate it, move it along the ground, and deposit it up to 5 feet away. This movement doesn’t have enough force to cause damage.

If you are dealing with a building that is explicitly sitting on "loose earth" then there is nothing in the rules that prevents this usage. However, that term is not defined in the rules and is thus subject to DM ruling on what exactly it applies to. I discuss this at length in my answer to your previous question on the matter.

Beyond the ambiguity of the term, it does seem unlikely that many buildings would be built on "loose earth". Especially a castle as you specify further in the question. Castles are huge and heavy buildings of stone with lots of people and vehicles as well to pack down the earth under it. It seems tenuous to consider any of it to be "loose". And that is, of course, assuming that it is built on earth at all and not on stone or cement or some substance like that.

There are also practical concerns like how much earth you can remove (assuming any) without it collapsing on or near you and how large of a hole you can make before that happens.

In short, if a DM rules that the material under a building is loose earth then you can at least attempt to create a sinkhole under it. However, the results of that sinkhole would also be at the DM's discretion. Talk with them about what you want to happen and what you are trying to do beforehand and they might give you an idea of how effective of a strategy it would be (if they allow it at all).