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Ambush

A vicious attack upon an unsuspecting victim.  By waiting patiently for the
right moment to attack, you are able to unleash a surprise attack, stunning
your target for 6 rounds and dealing 300 points of damage.  You must be
wielding a stabbing weapon for this attack to work.

The classes that get the skill ambush are:

thief      : Level  85 (excellent)
bard       : Level  76 (excellent)
assassin   : Level  75 (excellent)
ranger     : Level  16 (excellent)
rogue      : Level  75 (excellent)