Here are some changes I propose in order to better deal with the failed convert problem (better than giving a random convert, I mean). I believe this version of Mastermind also sufficiently discourages whisper-king-meta.
Can’t Touch This (Passive): Death immune. You never appear suspicious to investigative abilities. Nobody can take your place. Once you’re dead, there is no more Mastermind.
Little Bird (Day Ability): At the start of the night, learn whether the people that whispered your target today are convertable.
Dirty Work (Day Ability): At the start of the night, become Assassin.
Convert (Night Ability): Convert a player to the Unseen (1-day cooldown).
Foresight (Night Ability): Learn a player’s converted class type.
The Cult Leader
Blood of Mithras (Night Ability): Gain 1 use of eradicate at the start of the night. The sacrificed player will die at the end of the night.
This ability is obsolete since players can now suicide.
Blood Test (Day Ability): If a player is bleeding, learn whether they can be converted.
Rupture (Day Ability): Cause a player to bleed, they will die in 2 nights unless healed.
Brainwash (Night Ability): Convert a player to the Cult (1-day cooldown).
Eradicate (Night Ability): Kill 2 players.