Self Geass Scroll

A type of magical contract [curse contract] inscribed on parchment that is employed by magus. It is used only when making an arrangement that can never be broken, and imparts an “obligation (geass) curse” capable of binding the soul after death if the target possess a magic crest. In principle, the curse cannot be canceled by any means, acquiesce to bind such a contract is one of the greatest concessions a magus can make.

Translator’s Notes
  1. ^ Forced Contract with Oneself.
Fate/Zero Animation Guide II: Glossary of the holy grail war II