Final Fantasy VI Encyclopedia
Basic Weapon Stats:

Battle Power
A weapon's power determines how much damage you do when you attack with the weapon equipped. See damage calculation for exactly how a weapon's Battle Power affects the damage done.

Hit Rate
Hit Rate determines whether or not you hit when you attack with the weapon equipped. The higher the Hit Rate, the higher the chance to hit. See the chance to hit calculation for detailed info on how Hit Rate works.

Weapon special abilities and effects:

Randomly casts a spell
For weapons that randomly casts a spell when they hit the enemy, the chance that the spell will be cast is 1 in 4.

This spell can't be absorbed by Runic or reflected by the wall status, and costs 0 MP to cast.

If the spell that is cast can be blocked by Stamina (see step 5 in hit determination), then the chance to hit for the spell is determined as normal. Otherwise that spell always hit (see step step 3 in hit determination).

The damage done by the spell is determined as normal, with a few exceptions:

1. The spell does not ignore your row, so if you're in the back row it will do half damage. If the weapon that cast the spell ignores row, then the spell cast will still do full damage if you're in the back row.

2. The damage multiplier added by Jump affects the spell as well, so if you jump and it casts a spell then the spell does extra damage.

3. If the weapon does automatic criticals, then the spell automatically does a critical as well (even though spells normally can't do criticals). However, if the weapon does a critical because of the standard 1 in 32 chance, then the spell does not do a critical.

Only gains full power when Imp
Weapons with this ability: Imp Halberd
When a character is equipped with a weapon with this ability, they only get the battle power from the weapon if they have imp status, otherwise the battle power of the weapon is considered to be 0.

Deals normal damage from back row
Weapons with this effect: Illumina, Flail, Full Moon, Morning Star, Boomerang,Rising Sun, Hawk Eye, Sniper, Wing Edge, Cards, Darts, Doom Darts, Trump, Dice,Fixed Dice.
Weapons with this effect still deal full damage if the character equipped with the weapon is in the back row (i.e. skips step 4 of damage calculation). However, it still gets reduced damage if the target is in the back row.

Has a perfect Hit Rate
Weapons with this ability: Illumina, Heal Rod
Weapons with this ability always hit. (see Step 4b. in hit determination).

Randomly attempts to steal an item
Weapons with this ability: Thief Knife
Weapons with this ability have a 50% chance of attempting to steal as well as dealing it's normal damage. If it attempts to steal it is exactly as if the Capture command were used.

Damage is based on HP
This is the Atma Weapon's ability. Weapons with this ability have the following exceptions to standard damage calculation:
After step 9 in damage calculation, the damage is modified as follows:
step 10a. damage = damage * level
step 10b. damage = damage * ((current HP / 256) + 1) / ((max HP / 256) + 1)
step 10c. damage = (damage / 64) + 1
The length of the Atma Weapon is determined solely by the damage you do as follows:
Damage Length
0 - 500 Shortest
501 - 1000 Medium
1001 - 9999 Longest

This ability is ignored if you use the Capture command.

Ignores defense
Weapons with this ability: Atma Weapon, Valiant Knife
These weapons ignore the defense of the target, as well as many other steps in damage calculation. The steps skipped are: 5 - Damage Multiplier #1,6b - Defense Modifcation, 6c - Safe, 6d - Target Defending, 6e - Target's Row,6f - Morph (target), and 7 - Damage Multiplier #2.
This ability is ignored if you use the Capture command.

Randomly attempts to kill the enemy
Weapons with ability: Assassin, Striker, Wing Edge, Trump
Weapons with this ability occasionally try to kill the enemy. If the target is undead, then it is always killed, and then revived. If the target is not undead, there is a 25% chance that the Weapon will attempt to kill it. Stamina can block this (see step 5b in the hit determination algorithms).
This ability is ignored if you use the Capture command.

Deals double damage to humans
Weapons with this ability: Man Eater
If the target of a weapon with this ability is human, then add 2 to damage multiplier (see step 7 of damage calculation algorithms).
This ability is ignored if you use the Capture command.

Drains HP from the target
Weapons with this ability: Drainer
Weapons with this ability heal the attacker an amount equal to the damage dealt. Cannot do more damage than the attacker's max HP - current HP. If the target is undead, then it heals the target, and hurts the attacker instead.
This ability is ignored if you use the Capture command.

Drains MP from the target
Weapons with this ability: Soul Sabre
Weapons with ability do MP damage instead of HP damage, and heal the attacker an amount equal to the damage dealt. Cannot do more damage than the attacker's max MP - current MP. If the target is undead, then it heals the target, and hurts the attacker instead.
This ability is ignored if you use the Capture command.

Uses MP to deal critical hits
Weapons with this ability: Rune Edge, Ogre Nix , Illumina, Ragnarok, Punisher
These weapons Use MP to do automatic critical hits. The amount of MP used = [12..19]. If the attacker does not have that many MP, then no MP are used, but the attack is not a critical hit either (although it still has the standard 1 in 32 chance of doing a critical)
This ability is ignored if you use the Capture command.

Weapon is randomly thrown for more damage
Weapons with this ability: Hawk Eye, Sniper
Weapons with this ability have a 50% chance of having additional effect. The effect is that If the target has float status, then the weapon is thrown at the target, and 4 is added to the damage multiplier (see step 7 of damage calculation), If the target does not have the float status then 1 is added to the damage multiplier (see step 7 of damage calculation).
This ability is ignored if you use the Capture command.

Damage is based on dice rolls
Weapons with this ability: Dice, Fixed Dice
These weapons skill standard damage calculation algorithms and instead deal damage based on the dice rolls.
The damage for Dice = Dice Roll 1 * Dice Roll 2 * Level * 2. The damage for Fixed Dice = Dice Roll 1 * Dice Roll 2 * Dice Roll 3 * Level * 2.
For either weapon, if All Dice Rolls are the same then: damage = damage * Dice Roll.
For determining the dice rolls, each number does not have an equal chance of coming up. 1, 2, 3, and 4 each have a 18.75% chance of coming up. 5, and 6 only have a 12.5% chance of coming up.
This ability is ignored if you use the Capture command.

Deals more damage at low HP
Weapons with this ability: Valiant Knife
Weapons with this ability deals damage as normal weapon with the following exception:
After step 1 in damage calculation, the damage is modified as follows: damage = damage + (Max HP - Current HP).
This ability is ignored if you use the Capture command.

Randomly casts Wind Slash
Weapons with this ability: Tempest
When you attack with a weapon with this ability, there is a 1 in 4 chance that Wind Slash will be cast. This is not quite the same as magic randomly cast, and will not be disabled by the Offering.
This ability is ignored if you use the Capture command.

Randomly slices target hit
Weapons with this ability: Scimitar
This ability gives a weapon a 25% chance of slicing the target (killing it). Stamina can block this (see step 5b in hit determination algorithms).
This ability is ignored if you use the Capture command.

Randomly breaks
Weapons with this ability: Ogre Nix
Weapons with this ability have a chance of breaking every time you attack. The chance of breaking is calculated as follows:
if [0..(last digit of attacker's HP + 1)] = 0 then the weapon breaks.
This ability is ignored if you use the Capture command.