Gishki", known as "Ritua" (リチュア Richua) in the OCG, is an archetype of monsters released in Duel Terminal - Raid of the Inverz!!. Their team symbol is a blue sapphire mirror that all the members wear, usually around their necks or on their staves. The Ritual Monsters (and, starting with "Merrowgeist", Xyz Monsters) of the group all have "Evigishki" at the beginning of their names, with the name of the kind of creature they've become at the end.
Their Japanese name, "Ritua", is a corruption of the English word "Ritual", used in the TCG terms "Ritual Spell Card", "Ritual Summon", and "Ritual Monster". Their English name, "Gishki", is a corruption of the Japanese word "Gishiki", meaning "Ritual" in the same context as the TCG terms. The choice for the English name not only translates the play on words perfectly, but also prevents the need for explaining how cards with "Ritual" in their name aren't part of the archetype.
All known "Gishki" monsters are WATER, and many are Spellcaster, Sea Serpent, or Aqua. Their playstyle is focused on Ritual Summoning and either searching and returning cards to the Deck.
The "Gishki" archetype has three Ritual Spell Cards; "Gishki Aquamirror", "Gishki's Duplicate Soul Mirror", and "Forbidden Arts of the Gishki". "Gishki's Duplicate Soul Mirror" in particular is very unique, as it is the first Ritual Spell Card that allows you to use Life Points instead of Tributes for the Ritual Summon, allowing an easier way to call "Gishki" Ritual monsters.
