That is the correct spelling of the noun "duel" (a battle, more specifically by two opponents one-on-one).
The sound-alike word is the adjective "dual" meaning having two separate parts or actions (e.g. dual citizenship).
It is played with a duel runner and a duel board. The duel can be initiated without the consent of the opponent with a field spell Speed World. When a riding duel starts in a stadium the MC will shout 'Riding Duel, Acceleration.'
A field spell
The likely word is "challenge" (a test, contest, or duel).
sepent sortilla
In the film and the book it is Serpensortia.
The spell that Harry Potter used to cause Draco Malfoy to bleed continuously in the bathroom duel scene of "Harry Potter and the Half-Blood Prince" is called "sectumsempra".
Normally it would have to be poopus eatonium, but in a duel it would have to be crapeth eateth.
PRESS x ON THOSE LIGHT's YOU'LL SEE THE LETTERS ;)
You can Summon him in a Duel with the Ritual Spell Card, Novox's Prayer. But like all Ritual Monsters, his card is completely unobtainable outside of a Duel without hacking the program.
It means the millennium puzzle or a Spell Counter or Triangle Power.
When he is in his final duel with Harry Potter he attempts to kills Harry Potter with the killing curse with Dumbledore's wand (The deathly Hallow Wand) which should have been given to Draco but Harry beat Draco in a duel so he was the owner and Dumbledore's wand backfires when Harry tries the disarming spell so Tom Riddle gets hit by his own spell.
In real life you don't need a duel disk to duel.