Mafia 73. Forest Kingdom

how does it actually work? An orc comes to kill a unicorn, some magic triggers, and he ends up killing one of his own?

He cast an illusion, making the other orc believe that he is the unicorn. Or he blinded him with his horn, and the blind orc accidentally killed his accomplice.
Personally, I'm also in favor of the possibility of a mafia member killing his own allies; it's more fun.