It can be found in the Shadow Temple. Anything in the Shadow Temple is nightmare fuel. Anything. Wallmasters, skull-raping shrieking zombies, a mound of quivering white rotting flesh surrounded by long, bony arms with long, bloody fingernails that grab Link by the head and hold him in place until said mount of rotting flesh can slowly inch forward and attempt to bite his face off, rooms lined with skulls and bones, pools of acid, paintings that say things like, "Here is gathered Hyrule's bloody history of greed and hatred" and "What is hidden in the darkness... tricks full of ill will... you can't see the way forward...", guillotines over bottomless pits, wooden crosses with chains hanging off them surrounded by blood, a ferry with a prow that resembles the Grim Reaper which carries people to the underworld, and it's located in a graveyard.

And just to cap it off, it's most likely connected to the well in Kakariko Village (which is a mini-dungeon themed exactly the same that Link does as a CHILD). That people presumably drink out of. "Hey, does this water taste like evil to you?"

This game is rated E for Everyone 8D