Here is an extract of the game manual about how to use the weapons. As english is not my native language, there may be some mistakes, sorry about that !
2.4 The weapons : basics
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Weapons are of 4 different kinds : swords, axes, spears and warhammers. They can
be of different quality : basic ones for training, or made of iron, steel,
mithril, adamant or vorpal.
Every weapon, when used against a monster, provides the same basic damage, based
on your level and the weapon quality.
2.5 The weapons : advanced
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Every weapon has a special ability that you can use to multiply your
strikes, causing devastating wounds if you are a true master of arms !
2.5.1 Sword charge
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You can charge with swords to increase the damage you inflict. To do so, you
need to move in one direction for several turns with your sword, then hit a
monster in the same direction.
Sword charges, when succeeded, are indicated by the yellow blod message :
"Sword charge #n!" where n is the charge amount.
2.5.2 Axe whirlwind
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If you kill a monster with your axe, you will initiate a whirlwind attack, and
attack every monster around you, the first at 2x damage, the second 4x, and so
on.
Axe whirlwinds, when succeeded, are indicated by the yellow bold message :
"Axe whirl #n!" where n is the damage multiplier.
2.5.3 Spear charge
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If you kill a monster with a spear, you will charge in the same round on the
monster killed position, and if there is a monster next in the same direction,
you will attack it with double damage. If you kill the second monster, you will
charge and attack with 4x damage, and so on until there are no more monsters
aligned.
Spear charges, when succeeded, are indicated by the yellow bold message :
"Spear charge #n!" where n is the damage multiplier.
2.5.4 Warhammer charge
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When you hit a monster with your warhammer, there is a chance that you succeed a
warhammer charge (based on monster level and you warhammer quality). If you do
so, you will move one step ahead, and the monster will be pushed several steps
backwards. If the monster hits something or somebody while being pushed back, it
will be knocked for several rounds.
Warhammer charges, when succeeded, are indicated by the yellow bold message :
"Warhammer charge #n!" where n is the number of cells the monster is pushed
back.