Muggles' Guide to Harry Potter/Major Events/Nymphadora's Death

Overview
At the great Battle of Hogwarts, Nymphadora Tonks is killed in battle. Tonks was meant to be at home with her newborn son Teddy but came to assist her husband Remus Lupin who was also killed in battle.

Event Details
When Harry returns to Hogwarts, Neville, who is escorting him from the Hog's Head, has assumed that he is there to liberate Hogwarts from the Death Eaters, and uses the charmed Galleons that Hermione had created, to recall Dumbledore's Army. Presumably, a member of Dumbledore's Army who either was in the Order of the Phoenix, or whose parents were Order members, passed the word, because members of the Order start to appear through the tunnel from the Hog's Head as well. One of the Order members who we see arrive is Lupin.

After Harry has returned from Ravenclaw Tower, he finds that Ron and Hermione have left the Room of Requirement, saying something about a bathroom. As the whole school has now been summoned to the Great Hall, Harry heads there to see if he can find them. There, he hears Professor McGonagall sending non-combatant students home. Once only students who are of age are left, Order members at head table start assigning specific areas of defence. Lupin will head up the group that is defending the grounds.

Returning to the Room of Requirement in search of the final Horcrux, Harry is accosted by Tonks, who demands to know where Lupin is. Asked about their son Teddy, Tonks says she has left him with her mother Andromeda. Harry tells Tonks that Lupin is defending the grounds, and Tonks runs off to find him.

After Harry witnesses the death of Snape, Voldemort offers a cease-fire so that Harry can surrender to him and prevent any more loss of life. Harry, returning to the school, looks into the Great Hall and sees Lupin and Tonks lying among the dead.

While this is not mentioned in the book, the author has mentioned in an interview since its publication that Tonks was killed by her aunt Bellatrix Lestrange.

Notable Consequences
Tonks' death once again reminds Harry that his is not the only life that is being affected by Voldemort's reign of power. This reaffirms his decision to do whatever he needs to do to eliminate Voldemort.

Lupin's and Tonks' deaths have left their infant son Teddy an orphan. Harry must be deeply affected by this, being an orphan himself, and as godfather having no little responsibility for Tonks' and Lupin's child.

Analysis
As was mentioned in the article on the death of Remus Lupin, painful as it is, the death of Lupin is somewhat necessary to the plot. Given that, however, could not Tonks have been spared? Again, we are unlikely to find an answer; however, we can speculate. Any such speculation must be fueled, in large part, by observation of the characters of Remus and Tonks, as portrayed by the author. One thing that is very obvious to the observer is the fierceness of the love Tonks holds for Remus. She has repeatedly fought to keep him, and is now fighting alongside him. It seems very likely to us that if Tonks saw Remus' death, or found him dead, that would impel her into a berserk attack on the surrounding Death Eaters, caring nothing for her own survival if she could take some of them with her, which would greatly increase the likeliness of her own death.

That being said, it would not be thematically possible for one of the two to survive without the other; Tonks without Remus, or Remus without Tonks, would be a woefully incomplete half-couple, always around to remind Harry of what he had (in his own estimation) caused. We are at the end of the series; it is necessary to tie up all the loose ends, so to speak, and given that Lupin cannot remain, Tonks cannot be left to drag upon Harry's memory. Her death, painful as it is, allows Harry to move on after the death of Lupin, and allows the book and the series to come to a satisfactory close.

Greater Picture
As godfather to the now-orphaned Teddy Lupin, we can guess that Harry now feels that he has significant responsibility in his upbringing. We never do learn exactly what role Harry plays in Teddy's life, but we believe that it is not insignificant, as in the Epilogue, Harry's children refer to him as "our Teddy." As Teddy had been left in the care of Tonks' mother Andromeda, it is a safe guess that it was Andromeda who did most of the rearing of the young Teddy, with a fair amount of help from Harry and his family.