Hex-Sealed Fusion, known as Fusion Seal Organism (
The monsters in these series are Fusion Substitute Monsters that can be Tributed with other Fusion Materials on the player's field to Special Summon 1 Fusion Monster of the same Attribute as the "Hex-Sealed Fusion" monster. The "Hex-Sealed Fusion" monster itself is counted as a one of the materials via substitution: e.g. if the player wants to Special Summon "Gatling Dragon" with "The Dark - Hex-Sealed Fusion", they must Tribute "The Dark" and either "Barrel Dragon" or "Blowback Dragon", not all three. Moreover, this is not treated as a Fusion Summon, so if the Fusion Monster is subsequently sent to the Graveyard or banished, it will become unable to be Special Summoned back.