Lethargy is an affliction which causes its victim to recover balance from actions slower.
One way adventurers suffer the affliction is via the Serpent-class ability in their Hypnosis skill.
Another way is via the two-handed specialisation of the Weaponmastery ability mastered by adventurers of the Runewarden, Infernal, or Paladin classes. With this ability, HEWing either arm will give recurrent lethargy until such a time as all wrist fractures are cured.
Eating a ginseng root or a ferrum flake will cure the lethargy affliction.