I have been GMing for my skype Roleplaying group for about a year now and after our first AP (ROTRL) we are about to start Kingmaker.
Before we started ROTRL none of us had roleplaying/gm experience so we had rather standard characters. Now with our second AP we feel more secure to choose more challenging character concepts.
Now one of my player had the idea to play a deranged barbarian who sometimes hears voices in his head and is compelled to follow whatever they say. He wants me to play those voices by privately messaging him what they tell him to do.
Now while this can lead to crazy situations I find it difficult to find a way to not GMmetagame what the voices might randomly say depending on the situation.
The other issue is that the character and his actions should not overshadow or burden the others too much, so it needs to be subtle as well.
So that why I am asking for your advice how can I mechanically make this character concept valid and interesting without putting the spotlight on one player all the time?