The source collar and the larva also serve similar purposes.
I personally believe it’s more that source=larva=Bhaal’s heritage
It ties our protagonist together, grants special powers, and possibly will be a driving our heroes and companions forward, through the story.
Keep in mind this is not a traditional tadpole that turns host into Mind flayer After couple days. From what I gather from interviews it’s more of Captain America tadpole which will put you under Mind flashers influence if you accept its powers.
The Bhaal Heritage never specifically held you back or required you to do something about it in order to unlock your ability to play the game.
