Double dashes can be used to signal the interruption significant
information inserted in between an independent clause:
Comitatus---the honor code between the king and his army where
the king provided shelter and riches to his military men in exchange
for their loyalty and protection---is exemplified in the epic, Beowulf.
The unbreakable law binding together king and his warriors--comitatus---provided warriors an honorable reason to fight.
A single dash can be used after an independent clause as an
effective way to insert a significant insight of an interrupted thought.
Hrothgar tells Beowulf that it is important to remember that nothing
on Earth is forever, since everything belongs to God---even Beowulf’s
glory.
AVOID VAGUE PRONOUNS:
They were supposed to aim for heavenly glory ad rewards in the
afterlife. Beowulf, a true hero, knew this.