and just by the wording it seems like it cannot be used as a transport unless its for the archon and the court. And if it is a transport it is only for the court of the archon.
"The Dark Eldar Tantalus is a Heavy Support choice in a Codex Dark Eldar army, and also may be taken as a dedicated transport for a Court of the Archon."
I have also looked at the updated forgeworld vehicles list and it isnt listed as a transport. S,F,O,Tk.
Very confusing for me or maybe its just late.
15,000 Dark Eldar