Convert the sleeping gas trap to just “gas trap”, and make it scale based on the difficulty. Each individual trap releases a single type of gas; which type is partially dependent on the level difficulty. At low levels, they all emit sleeping gas like normal. At higher levels, they emit stunning hallucination gas like container traps, clouds of poison gas, and maybe even nastier gases that reduce speed or miasmas that cause illness.

An artifact, likely named “The Fast [something]”, which grants speed, but also prevents you from eating because fast also means to refrain from eating.

Artifact cloak of invisibility Death’s Embrace, which grants phasing, immunity to death effects, and half physical damage, but reduces speed.

Artifact quarterstaff Staff of Battle. Deals double damage to everything and grants very fast speed when wielded.

Red light, a y that has an explosion attack that causes paralysis. This is a reference to red lights in real life making you stop.

(There could also be green lights whose explosion gives a temporary speed boost, but since this isn’t harmful to the target it’s a sillier idea.)

Boots of fleeing: they give bonus movement points based on how many turns ago your last offensive action was (offensive actions are things that would fade an Elbereth underneath you). For the first several turns after combat they grant no speed bonus, then gradually scale up to full speed. This means that remaining in combat grants you no speed advantage but lets you travel very fast if you avoid it.

Replace the whole speed system with the one from Tales of Maj’Eyal, another roguelike. This has a strict concept of a “global speed”, i.e. a number of movement points you are given every global turn. Every possible action has an associated movement point cost, which allows for things like zapping a wand to take less time and be done more frequently than making a melee attack. This gets rid of the weird existing system where, in ToME terms, your most recent action defines how much global speed you get, particularly if riding is involved.

One way to start implementing this is to have all the action functions that currently return 0 for no time taken or 1 for time taken to instead return a bitmask of all types of actions taken: “moved”, “attacked”, “cast a spell”, etc. Then the main loop code that handles these return values deducts movement points corresponding to the slowest action in this bitmask.

Getting cancelled should end a bunch of magical effects:

• Invisibility (temporary or otherwise)
• Temporary speed
• Temporary monster detection
• Temporary protection from the spell

Because it’s a status effect with some downsides, make unicorn horns cure invisibility by removing it. Maybe temporary speed too.

Speed boots should give bonus movement points equal to their enchantment (or slightly fuzzed as +1 to -1 randomly) on top of, or rather than, what they normally give.

Blessed speed boots give you additional movement points equal to their enchantment. (If their enchantment is negative, they subtract movement points, to a minimum of 1.)

Hellfire from monster casting, being inspired by Ghost Rider, should in addition to ignoring fire resistance slow the player down, since it does spiritual damage that reduces the victim’s will to act.

Fix vampires shifting into fog clouds as an escape method because this doesn’t currently work with fog clouds being slow and easily killed.

• Normal fog clouds can still be slow, but vampshifted fog clouds should have their regular form’s speed.
• Fog clouds in general should be very hard to land a hit on, with “your attack passes harmlessly through” like a ghost nearly all the time (allowing critical hits only?), or all of the time, if you are not engulfed. Fog clouds that are fleeing, like vampires running away, will not engulf the player.
• If a vampshifted fog cloud is pinned down and has nowhere to go, it can pass through the squares of a number of monsters blocking its way and land somewhere else, provided that space is within a few spaces. This prevents the player from trapping it in a corner and beating it to death.
• At some point, the vampire must turn itself back to normal, and not stay in fog cloud form forever.

Artifact leash that always makes the pet it’s attached to slightly faster than the player so that it won’t lag behind.

A monster carrying a loadstone is slowed to half or 2/3 of its normal speed.

Sometimes, eating a quantum mechanic corpse and causing your velocity to become uncertain can give you temporary very fast speed instead of toggling intrinsic speed. (In variants that implement a player-side slow intrinsic, it should also be capable of giving a temporary quantity of that.)

Implement a player fear system that unlike many other proposals, does not take away agency from the player by paralyzing them or forcing them to flee using a predefined algorithm. Instead, it incentivizes the player to flee by making continued combat unattractive.

Create a new intrinsic called “Panic”/”Panicking”. Sources of fear (including existing sources of paralysis-fear, e.g. ghosts) give you temporary amounts of this intrinsic. While you are panicking:

• You have a large to-hit penalty, possibly making it so that you can only land a hit when rolling a natural 20. (Directly subtracting a large number from to-hit could still be overcome by wearing rings of increase accuracy and would be hard to balance the exact number.)
• You deal half damage for any attack you can make land.
• Ranged attacks have a high chance of misfiring in the wrong direction.
• Spells not in the escape school or designated as emergency spells (or healing spells, for variants that remove emergency spells) have a higher failure rate or are uncastable.
• Your skills may be treated as if they are the levels you started the game with.
• Your speed is slightly boosted (if possible, only your movement speed, not your general attack/item use speed).
• If you die, your death reason will have a “while panicking” appended to it.

Give a warning message when temporary speed is about to wear off.

Monks who have passed through all the “Student of X” titles may go back and speak to the Grand Master to choose an elemental specialization and receive a power related to it. Stone gives a physical damage reduction; Air gives a random extra movement point here and there and a rare chance of dodging an attack. Water automatically counterattacks melee attacks. Fire boosts attacking power or gives extra attacks.

If the demigod flag is set, increase the speed of all non-sessile monsters (by giving them extra movement points).

You can wish for time. This decreases the turn count a bit, or alternatively gives you a large amount of movement points so that time effectively stops for everyone else besides you for a while (like what SpliceHack’s scroll of time does).

Monster spell that either generally or specifically debuffs the player. It targets beneficial timing-out intrinsics you have, such as speed, detect monsters, and see invisible, and reduces their time remaining, possibly removing them outright. Does not affect permanent intrinsics or extrinsics.

Give a YAFM when you gain very fast speed from any source while hallucinating: “Gotta go fast!”

Speed boots’ speed is gently nerfed to be better than intrinsic speed, but worse than temporary sources.

The wand of speed, zapped at yourself, grants temporary very fast speed and does not grant intrinsic speed. Intrinsic speed can be gained from a non-cursed potion of speed, and a blessed potion will still grant temporary very fast speed. These would be more useful in a system where permanent very fast speed is unobtainable.

Monster speed system that tries to keep all the good qualities of 3.6.1’s while also not letting randomization make monsters super fast or super slow: add a 16 bit int to the monst struct, and every 12 turns set (speed % 12) of them to 1. Then on each turn, the monster gets (speed / 12) moves, plus 1 if the bit for that turn is 1. This 12-turn cycle would need to be phase shifted randomly per monster (probably using hashing based on monster ID) so that you can’t move-count based on the turn clock.

Research on an efficient algorithm to generate the series of 12 bits has found this, though it might be more entropy-efficient in the long run simply to generate all 4094 permutations of bits and randomly pick one with the correct number of bits whenever needed.

It should be possible to have monsters that are sessile but still get “movement points” to make active attacks. Lichens and spotted jellies are two good examples of monsters that could be like that.

Fleeing monsters may randomly get a few bonus movement points each turn.

Challenge mode in which all non-sessile monsters are faster.

Adjust NetHack’s monster speed system to accommodate the additional property that if your speed is greater than a monster’s, it is impossible for that monster to move 2 turns in a row before you get to act.

Various ideas to give the bonus from certain sources of speed only as a bonus to movement, not to getting more turns to attack, use items, etc.

• First, to classify: most agree that speed boots, intrinsic speed, and steed speed should be sources that only give extra movement opportunities, while polyform speed should give extra full turns. Less agreement on magical sources of very fast speed (the potion and haste self), but general opinion seems to be that these should also not be limited to movement.
• Add a second pool of movement points that coexists with regular movement points, but can be used ONLY for moving. Speed boots and its fellow sources add to this pool, and any unused points in it are discarded at the end of the player’s turn. When you make a movement, points are deducted from this pool before being deducted from the “core” pool. Note that this approach can cause core points to accumulate to the point where the player can eventually get multiple non-movement actions on their turn.
• Reduce the movement point cost if you are taking a movement action and have sources of movement-only speed. (This might interact oddly if general-purpose sources of speed continue to add movement points as usual.)

Boots with the random appearance of “hiking” slightly decrease the speed penalties if you are encumbered.

Monks get a small amount of free bonus movement points when they kill a monster bare-handed, and also gain a small amount of free bonus movement points while making movement actions and not wearing body armor.

Structure player speed on a four-tier system: normal, fast (available intrinsically), very fast (available extrinsically via speed boots), and extremely fast (available only via consumables).

Haste self or other extrinsic speed sources hurt your AC and/or to-hit.

Make the amount of bonus movement points from temporary speed directly dependent on its remaining duration, with it gradually decreasing back to normal as the speed wears off. Also provide diminishing returns where giving yourself more speed boosts on top of already having temporary speed gives you less extra duration than it otherwise would, until eventually you can’t get any more duration than 1 per turn. These bonus movement points should also stack directly with all other speed sources, and be visible to the user in the status bar.

Additional temporary effects accompany drinking a potion of booze. The effects wear off when the confusion does (so if you extend it by, say, drinking a potion of confusion, the effects are prolonged). There is consensus that there should be both positive and negative effects; all of the following have been proposed:

• A damage bonus, or even double damage
• Temporary HP
• An accuracy penalty (or a Dexterity penalty)
• Slight reduction of speed
• Temporary cold resistance (debatable; if possible it should probably make you not feel cold attacks but still take regular damage from them)
• Attacking an enemy makes you automatically keep fighting it until one of you is dead
• Monsters are treated as having higher charisma (currently no monsters are treated as having charisma at all, but this could also hurt or nullify your ability to refuse a foocubus removing your clothes)
• You may pass out when the confusion ends, and end up with a hangover when you wake up. (Not described what the effects of a hangover would be). You may also find yourself suddenly on a different level when you wake up.
• You are protected from gaze attacks due to not being able to focus enough to meet someone’s gaze.
• If you’re a dwarf, the effects get magnified
• If there is any such thing as a player-is-scared effect, it is canceled when you drink the booze and blocked while you’re under the influence. This goes for however long the confusion persists, so you can extend it by drinking potions of confusion if you want.
• Any AC from your armor is nullified (this would also contribute to monk “drunken boxing” proposals, since monks don’t usually have as much armor AC)

Instead of a mslow flag in the monst struct, use a signed char called “speedbon” which represents the amount of speed offset that the monster should have from its normal speed. This allows for more nuanced speed mechanics, like zapping a wand of speed monster or slow monster multiple times and having the effects stack.

Quantum mechanics’ hits toggle your speed instead of teleporting you if you have teleport control. (You already know your position, so your velocity must become uncertain.)

Water walking boots give you the same extra speed as speed boots if you are standing on water or a fountain.

Dragon with slowing breath. The effect stacks with previous effects of slowing breath.