Mines

Attackers who found a castle’s walls too difficult to batter down often attempted to undermine them by digging a tunnel underneath the walls and collapsing it, either by burning out the supports or filling the mine with powder and blowing it up. The main factor in mining is the amount of time required to dig. The following table gives the volume, in cubic feet, that a team of 10 miners can excavate in a single eight-hour shift:

Race of Miner	Earth	Soft Stone	Hard Stone
Gnoll, halfling, human	150	100	50
Gnome, kobold	160	120	60
Goblin, orc	170	130	60
Dwarf, hobgoblin	180	140	70
Ogre	300	200	100
Hill giant	600	400	200
Fire giant, frost giant	600	400	200
Stone giant	1,000	700	350

If a creature is not listed, pick the most appropriate type from the table. For example, elves mine at the human rate. The mine tunnel must be a minimum of 5' square plus an additional 5' for each size class beyond Small. For example, humans, orcs, and dwarves require a shaft 10' square. Stone giants require a tunnel 20' square.

When the mine reaches the wall, a gallery must be dug out underneath. The galley must be as long as the wall is thick, at least 10' wide, and at least 5' deep (more if the miners require a larger tunnel). Once the gallery is dug the supports can be fired and the 10' section of wall above the gallery must roll the listed saving throw or be destroyed; if the save fails, the adjoining 10' wall sections become damaged.

The gallery can be more than 10' wide, and an additional section of wall must make a saving throw for every extra 10' of gallery width. Smoke powder or gunpowder placed in the mine can reduce the wall’s saving throw. Twenty charges of powder reduce one section’s saving throw roll by –1.

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