One possible plot could be that Harry uses his magic in ways that are unexpected in the Middle - earth setting of Helm's Deep. Maybe he uses spells like 'Protego Maxima' to create a shield around the fortress, protecting it from the incoming orcs. He could also use the 'Accio' charm to bring weapons to the defenders when they are in need.
He could use his flying skills on a broomstick to scout the enemy. Just imagine Harry on his Firebolt, flying high above Helm's Deep, seeing the approaching army of orcs and relaying the information back to the defenders.
Gandalf originated from a higher spiritual plane. He was dispatched to Middle-earth with a purpose. His background involves being part of a divine order and having a responsibility to bring hope and resistance against evil.
Well, 'Death of a Citizen' is also among the best Matt Helm novels. It really sets the tone for the series. It shows Helm's skills as an agent in a world full of danger and mystery. The story is well - paced and the characters are well - developed.
Gandalf is a Maia. He was sent to Middle - earth by the Valar. He was one of the Istari, a group of wizards. His purpose was to guide and oppose the rising power of Sauron.
The fact that Gandalf is from the Ainur is a very important part of his origin story. Also, his transformation into the form of an old man is significant. It allowed him to interact more easily with the races of Middle - earth, like humans, dwarves, and elves. And of course, his being sent to oppose Sauron is a central aspect of his origin. It shaped his entire journey in Middle - earth.
I think 'The Ambushers' is quite popular among Matt Helm novels. It has exciting plots and engaging characters that draw readers in. The storylines in these novels are full of twists and turns, and 'The Ambushers' is no exception, with Helm getting into all sorts of dangerous situations and having to use his skills to get out of them.