It is the main incident of many of the sagas from which he drew.

It is one of the chief characteristics of early Teutonic custom-law, and along with "Cormac's Saga", "Landnamaboc", and the Walter Saga, our author has furnished us with most of the information we have upon its principles and practice.
Steps in the process are the Challenge, the Acceptance and Settlement of Conditions, the Engagement, the Treatment of the vanquished, the Reward of the conqueror, and there are rules touching each of these, enough almost to furnish a kind of "Galway code".
A challenge could not, either to war or wager of battle, be refused with honor, though a superior was not bound to fight an inferior in rank.

An ally might accept for his principal, or a father for a son, but it was not honourable for a man unless helpless to send a champion instead of himself.
Men were bound to fight one to one, and one man might decline to fight two at once.

Great champions sometimes fought against odds.
The challenged man chose the place of battle, and possibly fixed the time.

This was usually an island in the river.
The regular weapons were swords and shields for men of gentle blood.
They fought by alternate separate strokes; the senior had the first blow.