I am a new DM and I am wondering if my latest idea for a character twist is jumping the shark/adding too much into it or not. I am preparing for my second session in a week and I just had a crazy idea to make a brass dragon the party met to be a warlock (Hexblade from the UA). Storywise it'll make sense (one of the party is a Hexblade as well, sworn to a dragon slaying suit of armor and I was going to make this dragon sworn to the same one for reasons) and it is unlikely they will fight the dragon again. It is also a Young Dragon so won't be the most powerful thing out there.