Infernoid are an aggresive archetype of FIRE Fiend Type monsters that Special Summon themselves by banishing Infernoid monsters from the hand or Graveyard. They are similar to Dragon Rulers in that some of them (not all) can even Special Summon themselves from the Graveyard. In order to load up the Graveyard so that the player doesn't have to banish Infernoids from their hand, cards like Reasoning and Monster Gate are played to mill Infernoid monsters. Lightsworn cards are often used as well.
Infernoid monsters have a wide variety of effects that range from destroying and returning monsters, Spells, and Traps as well as big beaters that can attack twice per turn. With a loaded Graveyard, Infernoids are very dangerous and can end duels in a matter of minutes.