C1 House is one of the houses at the Assassins' Guild school. The current head of house is Dr Perdore. It is now used for day pupils.
Like B2 House, C1 was one of the original student houses in the guild, and also takes its name from the architects's design plans. There was been talk of changing the name to one more in keeping with the more modern houses, but this has been overruled by former old boys of C1, several of whom have gone on to become influential people and are determined to see tradition contented.