In a rogue's world, where dexterity is often the main focus, this amulet is a great supplement to their hit point score and their ability to make a successful Constitution saving throw. As one can imagine, grace and agility are two things a rogue should have in plenty, since stealth is really their purview in the party.
Not to mention the dagger gives the rogue advantage on initiative rolls, which is a valuable thing for them to have. One of the advantages of being an Arcane Trickster is being able to cast Invisibility when needed; other roguish archetypes don't have that going for them, but this dust can certainly help.
Anyone playing a rogue probably has some kind of leather armor equipped; anything heavier pretty much makes that high Stealth skill redundant! So, if the rogue already has a roguishly high Sleight of Hand modifier, then nobody's pocket money will ever be safe so long as these gloves are worn.
Since carrying a torch kind of invalidates sneaking around in the first place, a rogue who needs some visual supplements will want these at hand. If it's not, the rogue should work on getting there over the course of the D&D campaign, either by a feat or ability score improvement when leveling up...or by magical item.
And the best part of the Manual of Quickness of Action is: even if the rogue who reads it does have a 20 Dexterity, they'll still increase their Ex score by 2 upon completion of the book. Rogues can spend one of the ring's charges to succeed a Dexterity saving throw that they had previously failed, further enhancing their already possessed Evasion ability.
Looking through the glass highlights any hidden items (Weapons, money, vials of poison) somebody is hiding on them. A longbow made out of bone white wood that feels unnaturally light.
The first arrow fired from it casts silence (one minute duration) centered on where it landed, regardless of whether it hit the intended target or not. As a reaction to an allay taking an opportunity attack, you may activate the crossbow to fire a bolt at the enemy.
Possibly similar to a Ruby of the War Mage where it eats an attunement slot and takes at least ten minutes to attach to a weapon? A minor magic weapon, a classic Rapier in base form, can use a Bonus Action to change damage types while keeping other stats.
Maybe between the physical types for no cost other than action economy, and a number of daily charges to do a subset of elemental ones for one strike? A gold coin that seems to reflect light in an unnatural and mesmerizing way.
When interacting with someone outside of combat, you can begin playing with the coin (Juggling between fingers, flicking it between hands etc.) On a failed save, the target is stunned by the performance and is completely focused on the coin, ignoring anybody or anything around them.
Jump or fall from any height, as long as you land on the cloth, you take no damage. A bag of rocks that, when thrown, deal 1D4 damage and count as simple ranged weapons with the finesse property.
After it shatters it leaves no trace of its presence and the dagger magically reforms in the sheath. For 10 minutes, any creature unaware of your presence must make a DC10+CIA wisdom check or fail to notice you, regardless of line of sight.
As an action, a creature can press the button capping the Flash gang to open it and toss it up to 30 feet away. Dust immediately begins to spill out of the canister when it is opened, and upon contact with the ground it billows into a cloud that quickly takes the form of 3d4 armed goons.
These goons are fragile, simple constructs made of dust and are unable to attack, physically interact with the environment, or make sounds other than sinister grunting and chuckling. The constructs possess limited intelligence, and are capable of little more than obeying and reacting to the user’s words in a shady-looking manner.
Twice per day, the user can activate the blade, to cast Invisibility on the user as a 2nd level spell and to immediately be teleported 1d6+3 times 50 feet away in a random direction (1d4, on a 1, north, 2, east, 3, south, 4, west). In large size the rapier acts as an unnaturally sturdy ten-foot pole.
When attached to the thief’s face, it replaces the user’s nose with a genuine hog’s snout. They can now smell treasure within 200 feet, able to pinpoint gold, precious gems, and enchanted items with great accuracy.
It cannot be removed for two days after attaching, constantly oozes snot, snorts loudly, and sends the user’s appetite skyrocketing. The DM may require self-control saves to keep the user from stuffing his or her face with whatever is nearby (hogs will eat nearly anything, so feel free to get creative and gross with this).
If one dies, while having their belongings in the nether bag, the possessions are teleported to their nearest living relative, unless the last will doesn’t specify otherwise. If one overfills their inventory space in the bag, their contents, and only theirs are spilled around the nine tells.
Kine has an 8 of Spades that creates 8 knives dealing 1d10 damage to up to 8 targets in a cone. 10 of clubs might reveal a trap or weakness, confuse or blind a foe.
While attuned, the wearer of this cuff has access to a tiny pocket dimension, capable of holding one small item (no larger than 1 cubic foot). As a bonus action, the wearer can stow a small item from their cuffed hand into the pocket dimension, using a slight gesture.
When broken, the bead releases the smoke, which fills an area with 5 cubic feet. Anyone starting their turn in the smoke must succeed on a DC15 constitution saving throw, or is blinded for 1 minute.
Once thrown, the attuned wielder can use a bonus action to teleport to the dart’s location as per the Blink spell. You vanish from your current plane at the end of your turn, and appear at a random location in the Fey wild.
Crane: The baton transforms into a grappling hook attached to 100 feet of silk rope. While attuned, the wearer automatically reduces falling damage by half, and can use a reaction to make an Acrobatics check (DC15) to negate falling damage entirely, and move up to 10 feet upon landing.
A small weathered piece of rolled parchment contained within a case made from a human femur bone. When removed and consulted with a DC15 Dungeoneering check, acts as a live-updating map of the bearer’s surroundings.
When lit and smoked, the user comes under the effect of Gaseous Form for 10 minutes. All creatures within the vicinity, including allies, must make a DC 15 Wisdom saving throw at the beginning of their turns or forget about the wearer’s presence.
A whiskey tumbler that shows an X-ray view of a humanoids circulatory system when you look through the bottom of the glass. Seeing a creature’s heart rate through this manner gives advantage on insight checks to see if they are lying.
This special use of the knife causes it to disappear for 1d6+3 hours, and then it reappears in the attuned wielder’s possession. After it disappears, regardless of whatever actions the attuned wielder takes, a replacement weapon can be drawn for free.
The effective dosage is ten drops for an adult human of average weight. A person can be repeatedly paralyzed for as many doses as they’ve taken within the last 48 hours.
The second, ‘real turn’ actually occurs, but is not perceived by and cannot be reacted to by anyone who isn’t a deity or otherwise sufficiently removed from the mundane world. While you wear this cloak with its hood up, Wisdom (Perception) checks made to see you have disadvantage.
And you have advantage on Dexterity (Stealth) checks made to hide, as the cloak’s fur shifts to camouflage you. Additionally, the attuned can cast Invisibility once per long rest on themselves by using a power word.
When the command word is spoken and the container is opened, it reveals completely different contents. This dagger is a favorite among high profile assassins, as it cannot be found during a pat down.
Once inside the Dream, the user must pass an Intelligence (Stealth) check to stay undetected. They can make an Intelligence (Investigation) check to search and shape the dream to find the answer to one question.
While they are in this state, they can use the hide action to blend into the shadows cast by any object larger than they are (such as a building or a tree). Adds a +10 to speed when worn and allows the user to leave a creature’s range as part of their movement without invoking an attack of opportunity as long as they did not start their movement inside the creatures range.
When you twist the handle, it expands to a full sized pike and vice versa. A round, flat disk that, when thrown, will create a minor illusion to distract from looking at the thrower’s direction.
A container of dark sludge that camouflages the wearer against the night sky. A piece of paper that, when someone dead’s name is written on a line at the top, makes anyone who reads it thinks that it is the will/journal/letter/etc.