Yeah, he's an actual mech. No details about his fighting style yet, but I will tell you it won't matter how far away you are if you piss him off. Seems like you guys have the right idea.
One of the attacks I was prototyping was 3d20 take best. It won't appear on this Nineball that purely, but you have an idea now of the power this thing can use. Not every attack will be that powerful, and it won't be able to use an attack like that every turn. I forsee a little weapon-theft of dead players, as well... Hint hint, killing the Nineball is an all or nothing thing. Going to let you stew over that for a bit, but any mechanics that apply to you apply to it.
HP might be around that, yeah. I haven't fully fleshed out it's stats, but they're mostly arbitrary: it's going to have an armor and HP value at the very least, and everything else is mostly handled without rolls because it would be too high for most people to dent it. The armor dosen't work the same, either. Hit an attack with 1 damage and the armor takes that damage.
You're looking at a behemoth with about 6 attacks and 2 supporting abilities, by the way. This mode is called Nine Ball in reference to another infamous Nineball... and no, it's not a Touhou reference. I think one of you got it right.
Since you'll adapt strategies the moment this thing comes out, I'll hint at two of the six weapons.
One is a hand-held weapon capable of damaging any number of you, so long as you're within a certain range. It's 2d8 damage for anyone involved.
Another weapon is the "all-range" one, that can get you no matter where you are. It's not visible until it uses it, either. It does 2d20 average on d8 targets. The damage is split equally among the targets.