I am planning for the final boss of a major campaign arc for my group of 6 players (the Barleybrook Boys), who will be at around level 8 or 9 when they face the boss. They are fairly optimized, and I have been generous with ability score generation and magic item distribution, so they will probably hit slightly above their weight class. This is my first serious monster homebrew that will definitely see play on the table, so I would love some advice.
To give a bit of background, Phala Kuslov is a white dragon, given greater intelligence by an infernal artifact, who has taken human shape and gained control of the mercenary branch of a major criminal organization. This stat block represents her human form, which will be "phase one" of the fight and include a few minions (none higher than CR 3 or 4). Phase two will be against her dragon form and in her lair, with no minions but having to contend with lair actions.
I am looking for feedback on what I have created so far: is it too powerful, could it be amped up in some areas, do certain things need tweaking for clarity, etc. I would also love some other ideas to make the fight interesting! Mostly looking for some unique traits, reactions, and/or bonus actions that will make this fight not feel like whaling on a sack of hit points. I want to make it feel like she still has the power of an adult white dragon, even when in a smaller form.
Statblock created with Falindrith's Monster Maker, concept image created with Heroforge.