You can literally just suck your opponents Deck dry and leave them with bad draws for the rest of the Duel
Keys can be acquired in any of the following ways: If a location with a key on it has no clues, an investigator may take control of each of the location's keys as a If an investigator causes an enemy with a key on it to leave play, that investigator must take control of each of the keys that were on that enemy
So that's all guys

Attack!" When Marik activates that monster's effect, he announces, "Holding Armss effect activates!" When Marik Summons "Humanoid Worm Drake", a cut-in frame of Marik's face briefly appears, and he announces, "The Fusion Monster, Humanoid Worm Drake!" Most of the time when Marik attacks with that monster, he announces, "Attack, Humanoid Worm Drake!" followed by "Slime Drake! When Marik Summons "Legendary Fiend", a cut-in frame of Marik's face briefly appears, and he announces, "Legendary Fiend!" Most of the time when Marik attacks with that monster, he announces, "Legendary Fiend attacks!" When Marik activates that monster's effect, he announces, "Legendary Fiend activates its effect!" When Marik Summons "Revival Jam", a cut-in frame of Marik's face briefly appears, and he announces, "This shapeless being is utterly indestructible!" followed by "Revival Jam!" Most of the time when Marik attacks with that monster, he announces, "This plasma can transform into the sharpest of swords!" followed by "Attack, Revival Jam!" When Marik activates that monster's effect, he announces, "The perfect defense against any enemy attack!" followed by "Revival Jam gels back together!" When Marik Summons "Viser Des", a cut-in frame of Marik's face briefly appears, and he announces, "Viser Des!" Most of the time when Marik attacks with that monster, he announces, "Viser Des

Back then, the entire game fit into a single binder
In the video game its measured as Rads, and if you accumulate too many Rads, your stats begin to drop and eventually your character dies