Ritual Spell Cards are used to summon (usually powerful) Ritual Monsters. In terms of timing, they're played just like normal spell-speed 1 spells. Ritual cards will usually require that you tribute...
They are basically magic cards. They allow you to summon strong monsters, provided that you sacrifice the monsters that are specified on the card first. You can win them by defeating duelists who use...
You can get rituals from the graveyard slot machine from the following: Pegasus - Gharma Sword Oath, Curse of the Millennium Sheild The Labyrinth Ruler - Gate Guardian Ritual Yugi - Black Luster...
Obelisk the Tormentor (Effect Monster) is not Ritual Summoned nor does it require a ritual. To summon Obelisk the Tormentor, you must Tribute 3 monsters (it is treated as a Tribute Summon).