I’m going to preface this by saying I’ve never home brewed anything before. I’m completely inexperienced.

I am currently DMing a campaign with 4 10 year olds who are 6th level. They are approaching a big fight they have been waiting for a long time: Lord Narlif. Back when the campaign, Lord Narlif hired them to go on a quest to retrieve a single dragon toe from a goblin lair. A few levels later, they found it and came back to Lord Narlif. They had gotten some hints that Narlif was a bit fishy though. When they gave the toe to Narlif, he had them prick their fingers to “sign an acknowledgment of their transaction”. Truthfully, he had needed their blood and the dragon toe to basically harness the power of an old powerful dragon. He is halfway possessed, and is sort of like a humanoid with wings and dragon powers. He is not as powerful as a normal dragon though, and the PCs just learned that he is simply a ‘prototype’ for a necromancy group aiming to bring back the Era of Blood and Glory, where dragons reigned with a fiery fist.

Back to the point, I need to homebrew him so I can run the fight and I have no idea what to do.  Does anybody have any ideas? Advice?

Thanks in advance.

Have you looked into adding the Half-Dragon template to an existing monster? Here is that template applied to a Veteran so you can see the difference: Half-Red Dragon Veteran. If you added that onto something would that work?

You could also just run a wyrmling of whatever type and describe it as a humanoid. Might need to alter the bite a little if you want it to have a weapon.

Thanks for the suggestions! The wyrmling makes sense, as I would rather have more dragon features than human features. Altering the bite would allow it to make it seem more half-human like.