Fiends (悪魔Akuma; Chinese: 惡魔), known as Demon in OCG, are a monsterType consisting of cards resembling demons and devils, as well as many other vile, twisted, beasts or mischievous beings. Fiends receive a power-up from "Yami" (or the newest one "The Gates of Dark World") Field Spell Card, and since many Fiends are DARK, they also get a boost from "Mystic Plasma Zone". Many have effects that hinder or punish the opponent and many others require penalties from the user. Some Fiend cards work together while others Tribute themselves, other cards or payLife Points to use their effects. There are also a great number of monsters and spells that Summon Fiend-Type Tokens, which can be used either as Tributes or simple stall defenders. Fiends are most notably used by PaniK, and Yami Bakura and some of Yugi Muto's most well known monsters are fiends.
"Earthbound Immortal Ccapac Apu", one of the "Earthbound Immortal" cards, is also a Fiend-Type monster. Since it would require a Field Spell Card to remain on the field, a Fiend-based Deck would have even greater use for Field Spells such as "Mystic Plasma Zone".