The setup is this:
MM, Assassin, Convert (doesn’t matter which), Prince, Starting Good King.
The Unseen vote up the Prince when the King decide fate pardons.
The Unseen then vote up and executes the Good King
Prince jails and executes the Assassin
Loyalty triggers
Prince jails and executes the new Assassin
MM vs Prince 1v1
Prince jails and executes the MM
BD wins
Even if they no lynch the Prince can just execute the assassin and win the 2v2 with king.
This makes the situation unwinnable for Unseen even if the Prince is successfully tricked into thinking the King is evil to begin with.