Remove the ability of speed potions to always, reliably confer the speed intrinsic. Instead, you need to already have a lot (at least 100 turns) of temporary very fast speed before drinking a potion of speed will give you the intrinsic.

Red light, a y that has an explosion attack that causes paralysis. This is a reference to red (traffic) 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.)

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.

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.)

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

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.

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.

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.)

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

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.