Help Chain Lightning

Syntax : cast 'chain lightning' <target>

Chain lightning is a deadly spell, producing a powerful bolt of
lightning that arcs from target to target in the room, until its
force is fully expended.  Allies of the caster may be hit by this
spell if they are members of a clan, while the caster himself will
not be struck unless no other viable target remains.  Chain lightning
is most effective when used on groups of creatures.