In a formal duel, a second is a person who will act as a replacement for one duellist if necessary. A second is usually a trusted ally of the duellist in question.
In 1991 when Draco Malfoy challenged Harry Potter to a duel, Ron Weasley volunteered to be Harry's second, and Draco chose Vincent Crabbe to be his second. On the night the duel was supposed to take place, Draco and Crabbe never showed up, in the end it turned out to be a plan on their part to get Harry and Ron in trouble for being out of bed after curfew
Behind the scenes
- In the rules of real duels, each party to a duel had a second. Together, the seconds would determine a suitable "field of honour" where the duel could be held without interruptions. Seconds also ensured that the weapons being used were equal and that the duel was fair.