Cordati
A name for the manual governing the professional standards, protocols and etiquette demanded of an Assassins' Guild member. This may be another name for the manual described elsewhere as the Concordat.
Annotation
From the Italian 'cordati', the plural of cordate, English 'chordate', one of the links of the spine - indeed the family Chordata is that phyla of animal with a backbone. Hence this book must be the spine of the curriculum.