A Ritual Card is a type of card in some older video games that predate or otherwise do not follow the OCG/TCG rules. Ritual Cards are not Ritual Spell Cards; they are considered to be their own distinct card type, rather than a type of Spell Card.
Ritual Cards are color coded blue and used to Summon specific monsters, by sacrificing three other monsters from the field. The player does not need to have a copy of the Monster Card they are trying to Summon. If they do have a copy of the Monster Card, it can be Summoned without the use of the Ritual Card.