If a character is reduced to 0 Sanity, he undergoes Derangement.
The character immediately goes catatonic. The character may immediately test to escape catatonia. This is a Will + Nerve Test. The difficulty of the test, at this point, is 9. If the character succedes, he continues the Derangement process. If the character fails, he remains catatonic, and may test to recover again every 6 hours. The difficulty of the test reduces by 1 each time it is tested, but never below 1.
When a character comes out of Catatonia, mark a Derangement on their character sheet. This Derangement will have a Derangement trait associated with it. This is a mental disorder or disease that the character now suffers. The character is returned to one sanity, but remains Broken for 24 hours minus their Will Ability. After the character recovers from being broken, he regains half of his Sanity.