As Harry steps through the portal he realizes he's been a part of the world in his past and he's about to make sure that the one who caused his pain and killed his father figure would not survive what is to come.
A name, most don't know.
Unfortunately, there is no telling where and when a person ends up, only that you are where you are needed most.
Now what's a girl to do when you're in Middle Earth with nothing but the clothes on your back and a cheap blade in hand? She is Dwalin's adoptive daughter, he's taken care of her since he found her at the age of 10.