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Keywords are:  'thief skill vigilance'

Skill: vigilance                Lvl 12 Thie  (42%)
                                (helpful)   Requires: dodge
                                Group: Thief defensive fighting skills

This skill teaches thieves how to maintain a constant state of alertness
and readiness for danger.  It is used automatically when a thief is
attacked while sleeping, allowing them to quickly wake and sometimes
dodge before a blow even lands.

Thieves with this skill and knowledge of hide are sometimes able to spot the
subtle clues of possible hidden enemies allowing them to adopt a preemptive
stance in preparation for sneak attacks.

For those that have knowledge of trapping it may also reveal trapped exits,
doors and objects.