An Enchant Monster is a type of Monster Card created by Branch. The color of their card frame is red. These cards are placed in the Extra Deck.
Like other Extra Deck Monsters, Enchant Monsters cannot exist in either the hand or the Main Deck (even with card effects). If an Enchant Monster would be moved to the hand or Main Deck, it is returned to the Extra Deck instead. If a card like "Transmigration Break" or "Degenerate Circuit" is applying, the Enchant Monster would be banished rather than returning to the Extra Deck.
If an Enchant Monster is not Enchant Summoned first, it cannot be Special Summoned from the Graveyard or while banished (unless it specifies another way to properly Special Summon it).