Originally Posted by Neo Pikachu
Its good as one plot mechanic, but I think you need a lot more. Who might be opposing them, are these sisters even human, and who else might be seeking this artifact are all questions that you can possibly answer to give your plot some more dynamics. Further depth could be added by letting that artifact grant that power, but come with a cost, such as slowly changing them into something monstrous, causing the world they are in to become more and more blighted, or causing some other weird and strange effect that someone would want to stop before it gets too much out of control. Any crazy thing you can think of is fair game.
Alright, thanks for the tips :)
I was planning on them being bad and whatnot, and having a squad of people hunting them dow to stop them getting it, aswell as another group of people searching for the same artfiact but for different reasons. But thanks for all the other ideas, like making the sisters non-human, and having the artifact come with a cost. Thanks :)