Aura Monsters (オーラモンスター, Ōra Monsutā) are new monsters used in XXX. They are Special Summoned by Aura Summon. They are stored in the Extra Deck and the color of their card frame is dark red to differ from Composition Monsters, who are a classic red.
The Aura Monsters use a unique method of saying which materials they use; they use a "codename" instead of a line of which materials they use, and you have to banish monsters from your side of the field and Graveyard whose category of monster (Ritual, Effect, Fusion, Synchro, etc.) matches one letter of the codename. Remember that the maximum of monsters you have to banish from the Graveyard this way is 3. Example is that, if there is a card whose "codename" is FRIEX, you need to banish a monster whose category of monster starts with F, then with R, then with I, then with E and then with X. The codename should have at least 2 letters, with the maximum being 8.
An Aura Monster cannot be used as an Aura Material for the Summon.
An Aura-oriented deck is possible to use monsters of different mechanics to produce, in order to have the spectrum of mechanics needed for the Summon.
In case a card is a Pendulum, Shift or Snare monster, but it is part of another mechanic (e.g. Xyz Pendulum, Fusion Shift or Synchro Snare), then you can use that card as any letter of those it belongs. Example, an Xyz Pendulum can be used as either X or P for a codename of an Aura Monster.