The first mask it's

Cute!

Sabes qué es tenebroso, al saber que las máscara son en realidad los monstruos de los cadáveres.

@dragoncima13

Technically, the mask that you receive from defeating the monsters are actually the four giants of Termina trapped inside the masks. Every time he defeats them, he frees the giants. The corpses as you say is still alive. They only come back to life when they are put side by side with the Majora's Mask just to be defeated again by Link. Even quicker if Link equips himself with the Fierce Deity Mask.

This game is dark! About as dark as Twilight Princess and Breath of the Wild!

@Lylatroid

Those games are not the only games that are dark though. Adventure of Link is pretty dark too. Especially if you read from the manual.

Taking the plot of from the manual, the reason Zelda is in a sleeping spell is that her brother tried to force his sis to tell him his recently deceased father's secrets concerning the Triforce. She refused and the prince's wizard friend, angered by her refusal, tried to strike her down with a spell. He's successful in putting her in a deep sleep, but at the cost of his own life. The prince, feeling remorse and can't remove the spell off of Zelda, placed his sister in the castle tower hoping one day she'll awaken. He decreed that princesses that are born to the royal family from that point on would be named Zelda, in rememberance of the horrible tradedy happened that day.

And the main reason why Ganon's minions go after Link is because they want to kill him and sprinkle his blood on Ganon's ashes to revive the King of Darkness. Creepy huh?