ach of a character's skills and other proficiencies has a percentile value which defines the character's aptitude. Most will start between 15% and 30% at the level they are gained, though some start higher at level 1, based on race or class. Prior to reaching the minimum requisite level, a character cannot use a particular proficiency at all; characters with more than one class may have different requisite levels for the same skill or spell, in which case it will be acquired when either class reaches its requisite minimum level. The percentile score determines the chance of the skill working successfully each time it is attempted.

ach time a skill or other proficiency is successfully utilized, the character has a chance of becoming more adept in it, gaining an extra 1% to the aptitude score. The chance of becoming more adept varies based on the skill's difficulty and is also affected by the character's wisdom attribute and by a random element. The more a skill is successfully used, the greater the chance of its user's aptitude improving. All skills are closed-ended—there is a maximum aptitude that can be reached, usually between 80% and 100%, based on the character's class, number of classes, and the specific skill. On achieving this score, a character has mastered the skill and can gain no further aptitude increments by using it. However, all skills can also be augmented by equipment, and a few by spells such as Spider Climb.

Proficiency aptitude scores can also decrease, if the character dies, is Feebleminded, or is drained by use of the Energy Drain spell or certain mobiles' special attacks which duplicate it. The higher the character's aptitude in each skill, the greater the reduction will be. High-level characters also lose more skill when they die or are drained than low-level ones, though everyone suffers equally from Feeblemind. Once reduced by death or draining, aptitude scores can only be increased again by enough successful use of the relevant skills or spells.

he following skills may be learned on Mozart Mud: Alchemy, Appraise, Assassination, Axe Throwing, Axes, Backstab, Bandage, Bash, Berserk, Blind Fighting, Block, Bribe, Case, Catch, Climb Walls, Cobra Strike, Cooking, Crit Hit, Dagger Throwing, Daggers, Dart Throwing, Disarm, Dodge, Double Backstab, Dragon Claw, Draw, Dual Switch, Dual Wield, Eagle Claw, Endure Hunger, Endure Thirst, Extra Attack One, Extra Attack Two, Extra Attack Three, Extra Attack Four, Extra Attack Five, Extra Attack Six, Extra Attack Seven, Fanaticism, Feign Death, Find Death Traps, Find Hidden Doors, Fleshtaint, Gift of Pain, Greatswords, Guard, Hammer Throwing, Hammers, Heroism, Hide, High Swordright, Hitall, Instant Stand, Iron Fist, Kiai, Kick, Lightning Strike, Listen, Lose, Maces, Meditate Cleanse, Meditate Heal, Meditate Ki, Mind Over Matter, Mirrormagic, Mountaineering, One Finger, Palm, Parry, Petals in the Wind, Pick Locks, Plant, Pole Arms, Quivering Palm, Read Magic, Rescue, Rushing Bull, Safe Fall, Scan, Scrollcraft, Seven Drunken Fairies, Shadow, Shadowcast, Sneak, Inside, Sneak, Outside, Spear Throwing, Spears, Spellcraft, Spot, Star Throwing, Staves, Steal, Strobe, Stun, Stunned Maneuvers, Swimming, Switch Opponents, Swordright, Swords, Three Finger, Tiger Claw, Toss, Track, Unarmed Combat, Waves in the Grass, Weapon Kata, Whips, and Willow Dance.