Fate/stay double is a Play-by-Post RPG based on Fate/stay night. It takes place in an Alternate Universe, where all of the servants and several of the masters are different. In addition, the Holy Grail summoned twice the usual number of servants.
The servants are:
- Saber Class: Miyamoto Masami and Hervor.
- Archer Class: Odysseus and Atalanta.
- Rider Class: Mulan and Agrona, Celtic War-Goddess of the River.
- Berserker Class: Lancelot and Sigmund.
- Caster Class: Matou Kariya and Kaguya-hime.
- Assassin Class: Jack the Ripper and Hassan-i Sabbah.
- Lancer Class: Caenis of Thessaly and Lugh.
- Anyone Can Die: More than half the cast is expected to die by the end of the RP.
- Beware the Nice Ones:
- Aimi is part demon.
- Despite being an adorable, shy loli, Jack is still a serial killer.
- Crossover: Characters from both Fate/Zero and Fate/kaleid liner PRISMA☆ILLYA are in this RP.
- Easy Amnesia: Kariya has conveniently forgotten his past after being summoned as a servant.
- Hate Plague: One of the effects of Atalanta's Disputed Spoils of War.
- Historical Gender Flip: Considering this is a ''Fate/stay night' rp, a few of the servants were guaranteed to be this.
- Strongly Worded Letter: One of Atalanta's Noble Phantasms. Of course, the letter's addressed to Artemis and Apollo and whatever the content of the letter is, they aren't exactly pleased by it.
- Training from Hell: Takako's uncle puts her through this. However, the training is needlessly cruel; and hardly teaches her anything. Its real purpose is to make her as miserable as possible.