Zapping a wand of locking or casting wizard lock at a pile of rocks will turn it into a wall, or possibly a boulder if creating walls is too powerful.

A potion of growth (or “embiggening”), which lets you temporarily lift boulders, and a potion of shrinkage, which lets you get through narrow diagonal gaps if you would normally be unable to.

The “Construction Patch”:

• When digging out stone (not necessarily walls) with a pick, rocks may fall on your head with a lowish chance, about 10% per dug square. These deal the least damage if you are wearing a dwarven helm, and a little less than normal if you are wearing some other hard helm. Dwarvish characters have a high chance of dodging the falling debris entirely. Possibly also allow a boulder falling on your head from digging similar to when monsters tunnel.
• You can apply rocks at an adjacent floor square to build a wall. It takes 50 rocks, or 25 if there is a boulder in that square. (If the space is marked as being wall-nondiggable, this either doesn’t work, or flips the space to being diggable.) It takes 1 turn per rock to build it. In the process it creates an immovable object or dungeon feature called “partially-built wall” on that space, which tracks how many rocks are part of it. If you move onto the space, you can dismantle the wall and retrieve the rocks.
• You can apply rocks at an adjacent pool or moat to attempt to fill it. The more rocks, the higher the chance of filling it. This takes only 1 turn.
• Stone to fleshing diggable wall turns it into huge chunks of meat.
• Force bolts from striking wands or the spell scatter rocks off diggable walls they hit, and in roughly 5 shots the wall is destroyed.
• Digging a pit or hole puts a pile of rocks on a random adjacent square.
• When you dig a hole and fall down to the next level, you are usually accompanied by a shower of rocks falling on and around you. Dwarves are more adept at dodging and getting hit by fewer rocks.
• When using a pick to dig a square of natural stone where the four orthogonally adjacent squares are all dug out already, you are asked if you want to carve out a boulder. If you say yes, a boulder is deposited on the new space.

Note that the two boulder-creation methods above run the risk of being exploited for abusable quantities of food if you have stone to flesh available, and the stone-to-flesh-walls method explicitly invokes this.

You can pour a potion of oil over yourself to temporarily block any invisibility for 200 turns. While oiled, you take double damage from any fire source, and you can slip through boulders diagonally without worrying about how much stuff you’re carrying.

Add a frustration counter to certain boss monsters, which increments every time they want to close to melee distance with you but are unable to. Once this gets sufficiently high, they become capable of dispatching or shoving aside monsters (even if they aren’t normally) and breaking boulders to get to you. Different bosses have different thresholds for when this happens.

This prevents you from trivially using a boulder fort to shut down bosses like Master Kaen while you slowly whittle them away with ranged attacks, but allows you to employ strategies like that for a limited period of time.

Falling rock traps can dump multiple rocks onto you at once, up to (depth/4). Damage is taken for each rock. If a trap would drop 4 or more rocks on you, it may instead drop (rocks/4) boulders on your head instead. Helms should be less effective at reducing damage from falling rocks, and almost useless at reducing damage from falling houlders.

If multiple boulders are dropped, they might be dropped on nearby spaces as well, so that a pathway might end up blocked.

If you kick a boulder as a giant-race hero (or while polymorphed into one), it starts rolling across the ground as if it came from a rolling boulder trap.

Some falling rock traps (particularly deeper in the dungeon) contain one or more boulders instead of rocks.

If you trigger a rolling boulder trap for which a boulder didn’t generate because there was no room to put it, a boulder may fall out of the ceiling instead (and the trap is removed) similar to a cursed scroll of earth. On early levels, it doesn’t have to fall on the same square as the trap.

Also, rolling boulder traps (beyond early levels) that do find appropriate launch locations may generate with no preexisting boulder on one of those positions. When triggering the trap for the first time, a boulder drops out of the ceiling on one of the launch positions and then begins rolling across the trap.

Prevent giants from accidentally moving on top of a boulder in Sokoban, which incurs a luck penalty. This is probably most easily done by only allowing them to move on top of an unpushable boulder by prefixing the move with m.

Another possibility is just to prevent giants from stepping onto boulders in Sokoban at all, giving a message “The ceiling is too low for you to step over this boulder.”

Master Kaen should be able to smash boulders in his way, so that the player can’t easily defeat him with a boulder fort.

When hallucinating and pushing a boulder, the word “boulder” should be replaced in the message with a random object. Possibly this should be extended to any message using xname() to format an object.

If you attempt to push a boulder onto a space where a pet is, it will automatically move out of the way if there is an available space to move to. If not, it stays there and the boulder can’t be pushed. This may or may not cost the pet a move.

If a boulder rolls over certain types of comestible, it becomes a pancake. (Which types of comestible isn’t specified; probably it should not be possible to turn corpses, tins, or lower-nutrition-than-pancake permafood into pancakes.)

Giants can catch moving boulders (whether rolling along the ground or thrown), putting it directly into their inventory.

Thrown boulders behave like boulder traps: they keep moving even after they hit something rather than stopping and falling to the floor at that location. Possibly this is flavored as the boulder hitting the ground on the first target and continuing to roll in the same direction.

The player (and probably all creatures Large size or smaller) gets knocked back 1 tile when hit by a boulder (thrown or rolling).

Within Sokoban, boulders weigh 6000 for giants, just like anyone else, so you can’t carry them around.

For variants that have giants as a playable race: A giant who uses the m prefix before moving onto a boulder will step onto that boulder without pushing it, whether or not the boulder has been pushed up against a wall. (Monster giants step over boulders not against walls all the time.)

Randomly generated puzzle mechanisms that reveal secret doors once completed. Things such as finding a mechanism hidden under a statue, or having a boulder generate in a room and needing to push it somewhere else in that room.

Pushing a boulder costs d3 or d4 nutrition, in order to balance out its easy source of Str exercise. However, something would probably need to be done to compensate in Sokoban (maybe put even more food there?)

Boulders falling on the player’s head deal more damage than they currently do, and they don’t really have their damage significantly reduced if the player is wearing a metal helmet.

Rolling boulder traps don’t expect a boulder at a specific spot: they look up to 9 squares in all 8 directions for boulders, and the first boulder it finds will be triggered. If no boulder is in range, it may create one by dropping it from the ceiling in a suitable location, then rolling it across the trap (but only one boulder per trap will be created like this, and some traps generate incapable of creating a new boulder).

Rolling a boulder on ice makes it slide for up to 10 squares (provided it keeps sliding over ice) before stopping. If it hits some other non-ice walkable terrain, it stops immediately on that square. It is treated like a rolling boulder trap, capable of hitting monsters in its path. This mechanic could be used in Sokoban to create interesting puzzles.

Boulders deal 5d4 damage instead of 1d20.

Zapping a digging ray upward may either detach a boulder from the ceiling, or several rocks, instead of a single rock. If several rocks are released, each gets a separate damage roll.

Water nymphs may create a pool on their spot when killed. Items they stole from the player fall into it, of course.

Wood nymphs may create a tree on their spot when killed, and mountain nymphs may leave a boulder.

Boulders tear through spider webs (whether from a rolling boulder trap, thrown by a giant, or pushed by the hero). For extra realism, the web slows its momentum.

Wearing gauntlets of power, you can snag a boulder and pull it with a grappling hook. If in Sokoban this incurs a penalty.

Monks can forcefight or kick boulders and break them with high enough Strength.

The rocks generated by smashing a boulder or statue should never weigh more than the boulder or statue.

You can carve statues from boulders with a pick-axe.

A boulder that falls on top of an altar destroys that altar.

You can roll a boulder into the same square as a non-trapped flying monster (which doesn’t interact with it at all).

Falling boulders (e.g. from scroll of earth) will smash fragile items lying on the ground on the square they drop on. Possibly rolling boulders do this too.

Grand Master martial arts skill allows you to (attempt to) force-fight boulders and statues to shatter them with your bare hands.

More harassment effects: the chance of respawning the Wizard is a fixed 1/7 and the rest of the effects are equal probability. Multiple non-duplicate effects may happen at the same time.

• Unchanged: curse items, summon nasties, vaguely nervous, aggravate monsters
• Darken much of the level, and extinguish, destroy, or cut the remaining lifetime of light sources. Maybe also blind the player.
• Drop boulders around the upstairs, or iron bars.
• Spawn pools centered on the player, with sea monsters in them.
• Spawn lava around the level, not under the player.
• Create a hole or pit under the player.
• Create a stinking cloud centered on the player.
• If you are carrying the Amulet, it teleports to a random square on your level or the level below.
• If you are carrying the Amulet, it (and possibly any fake Amulets) becomes heavier. This either lasts until the next harassment triggers, or is permanent but the total amount of weight added to the amulet has some sort of cap on it. This is interesting primarily because it targets carry cap, which is a valuable end-game resource.
• A variety of powerful player debuffs such as dealing half damage, taking double damage, blocking HP or Pw regeneration, super hunger, etc.

When a boulder drops on a tile containing another boulder, it tries to roll to an adjacent tile. If it can’t (because all adjacent tiles have boulders or are walls), it drops as a second boulder like normal.

Don’t allow giants to carry an infinite amount of boulders.

Add a boulder-throwing skill for giants. Like other skills, its skill cap is determined by your role.

Monster spell that creates a wall, or possibly just a boulder, to block the hero’s progress.

Archeologists should be immune to rolling boulders.

You can #force boulders where there is a monster behind the boulder to displace it, or crush it if it is in/on a pit or a hole. Based on Strength, only works if monster is medium or smaller. Always displaces unsolid monsters, of course.

Since boulders are round (clearly so; any character regardless of low Strength can roll it easily), and corridors are presumably not round, you can always squeeze yourself into the opening between the boulder and the corner of the passage. Inventory weight does not matter, because any reasonable character would push their knapsack through the opening first, rather than trying to go through while carrying it.

A way to search for hidden passages behind a boulder you are pushing.