The Thief Tools are a set of technique items unique to Duster in Mother 3. All of them cause in-battle status effects on enemies, and several are comparable to PSI skills that Duster, a non-PSI user, cannot learn. Some thief tools have a fixed probability of success regardless of the enemy. Others have a base success rate which gets modified by an enemy's base resistance; these stats interact according to the formula Actual Success Rate = (Base Success Rate) x (Enemy Weakness) / 100. For example, Wall Staples have a base success rate of 100, and an Arachnid! has a wall staple weakness of 75. Wall Staples will therefore succeed against an Arachnid! 75% of the time.
In Mother 3
Duster first uses the Wall Staples in Chapter 1 to assist Flint and Boney in ascending a steep cliff, and can also use them in battle at that point. He acquires the remaining tools at the beginning of Chapter 2, when Wess sends him to Osohe Castle, and retains them for the remainder of the game. As they are functionally key items, they take no inventory space and are not lost in Chapter 7 after the Master Eddy fight.
"Only Duster can nail these wall staples into certain walls. The staples become footholds that allow everyone to climb to places previously thought to be inaccessible. Once the wall staples are set, they last forever."
In-battle only, makes one enemy cry uncontrollably. Smoke Bomb has a base success rate of 85
"Throw it against the ground to break it open and release smoke from within. The enemies may have a hard time attacking through the smokescreen."
"Explodes into an acrid smoke, bringing an enemy to tears."
"Staring at this may induce a sleepy trance. Be careful to divert your own eyes when using it."
"Sway it in front of an enemy to lull it into a deep sleep."
In-battle only, makes one enemy turn around and make them waste one to two turns, depending on if Duster is faster than the enemy. Siren Beetle has a fixed probability of success, working about 75% of the time, and most bosses are immune. It will always fail against enemies that cannot be approached from behind/enemies that lack a back sprite.
"Raised by Wess. It isn't silent, it's a siren, and this stag beetle will give off a piercing sound. Perhaps some animals are weak to this sound."
"A beetle that makes a shrill noise. Causes an enemy to stop and cover its ears."
In-battle only, lowers one enemy's offense (comparable to Offense Down α). Scary Mask has a fixed probability of success, working 70% of the time. The first use will reduce the enemy's offense by 20%, the second and third use will reduce offense by 8%, and subsequent uses will fail unless the enemy raises its offense.
"Put this mask on, and no matter who you look at, you're sure to shock the "Ack!" right out of their attack."
"Scares an enemy, lowering its offense."
In-battle only, lowers one enemy's defense (comparable to Defense Down α). Tickle Stick has a fixed probability of success, working 70% of the time. The first use will reduce the enemy's defense by 20%, the second and third use will reduce defense by 8%, and subsequent uses will fail unless the enemy raises its defense.
"Koochie koochie koo! Use this stick to tickle under the arms of your enemy and they'll naturally drop their rock-solid guard."
"Tickles an enemy, lowering its defense."