From the introduction:
Before the game starts, hand each player an index card. On each index card, write your name, 10 hit points, the name of the Danger (A Big Red Dragon, Room Full of Spike Traps, Cave Full of Goblins) and three things that Danger can do (Breathe Lots of Fire, Cast Spells In An Eldritch Tongue, Call For The Guards).
Shuffle the cards and select one at random.
The player written on that card is the MC.
Everyone else is an Adventurer.