When a character is vanquished with a spell dome of shadows cast by him does it stop?
Will it finished if the character is dead. Is my only option to unravel the thread or change of scene.

It is Duration: Scene, so it'll be up for the Scene.

I would say that if the character who cast it died, the spell is dismissed as it no longer has any connection to the source. Vanquished is just 'out of the fight' temporarily.

John