Prophet's Grav-Throne Tau Hover Chair Popemobile is basically the mobility scooter used by only the most wrinkliest of Ethereal ballsacks.
Due to being seen as a status for the Ethereal Supreme, the Hover Chair is leagues above the pitiful Floating Roombas used by lesser Ethereals. There doesn't seem to be any energy shielding placed in the Hover Chair as the fluff was vague on the details, what we do know is that it didn't really matter when a rampaging Culexus Assassin was busy tearing Aun'Va a new asshole.
Compared to the awesome Pulpit of Saint Holline's Basilica from the Sisters of Battle, the Dais of Destruction from the Dark Eldar and the Dais of Dominion from the Necrons, the Popemobile is an incredibly lameduck equivalent for the Tau, lacking in any form of weapons of even defence for that matter. We also ain't joking about it being a mobility scooter, seriously, look at the drive mechanism.
It's literally a mobility scooter. Whilst the bulkiness grants Aun'Va 6 Wounds, his movement range is the same as his troops at 6". It is really pathetic. It just makes you wish that his popemobile was equipped with twin-linked Fuel Rod Cannons like the Prophet's floating throne in Halo right?