Ritual Monster

Ritual Monsters are Monsters that can only be Special Summoned with its corresponding Ritual Spell Card. Such Examples include Relinquished, Black Luster Soldier, Dark Magician of Chaos, and The Masked Beast.

When a Ritual Monster is Special Summoned via its Ritual Spell Card, Tributes must be offered either from your side of the field, or from your hand, that either or exceed the number of stars present on the Ritual Monster Card.

So, for example, if Relinquished was Special Summoned via the Black Illusion Ritual Card, Only 1 Monster Star is required, so any Monster could be offered as a Tribute, since you cannot have a monster with 0 stars. However, with Black Luster Soldier or The Masked Beast, 8 Stars are required, so you either need to Tribute a few low-level mosters (With around 3 or 4 stars), or one powerful card with 8 or more stars.

If a Ritual Monster Card is discarded to the Graveyard (Say, with a cards like Delinquent Duo, or Graceful Charity), without it being summoned with the appropriate Ritual Spell Card beforehard, that card cannot be Special Summoned from the Graveyard with Cards such as Premature Burial, Call of the Haunted, or Monster Reborn.