From BoLS by way of Faeit:
The Ghostkeel is an elite choice that comes with 2 stealth drones for each Ghostkeel. It’s a Jet Pack Monstrous Creature, and you can take 1-3. It has the normal Tau BS 3 with 4 wounds, but only a T5. However the 3+ save with +2 to it’s cover save outside of 12″ should make up for it.
The main gun- Fusion Collider is an 18″ S8 AP1 melta blast gun that can be exchanged for a Ion weapon that is more infantry based with a S7AP4 Assault 6 gun that can overcharge for additional strength and a large blast.
It also has a twin- linked flamer that can be exchanged out for a TL bust cannon or fusion blaster.
The model has gear that doubles the cover saves to a max of +2 but also gains shrouded from it’s drones. It seems powerful with stealth, shrouded, and the limited doubling, but I have not had time to read the details to see what stacks.
Two support systems are also allowed for upgrades. Cost wise its a little over a hundred and a quarter.