Board Thread:Role Ideas (Mafia)/@comment-37502593-20181211221416/@comment-35356104-20181212083723

Source: https://town-of-salem.wikia.com/wiki/Making_New_Roles
 * Kidnapper/Mafia Jailor - Any roles that is similar to Jailor is an automatic rejection because because it is too OP and would cause paradoxes, like if both of them jailed the same person or Jailor jailing Kidnapper or Kidnapper jailing Jailor or both of them jailing each other.

Mafia Killing: Mafia Killing roles kill for the Mafia (pretty straightforward). The Mafia can only kill one person each night, and this should not change with the addition of a new Mafia Killing role, so you must keep this in mind and balance around it. The mafia’s strength lies in knowledge, not in sheer power. It is recommended that you do not try to make a new Mafia Killing role unless you are sure it is balanced.

Source: http://www.blankmediagames.com/phpbb/viewtopic.php?f=27&t=86493

I hope these explain :)