Queen Azshara allows you to choose an Ancient Relic.
If you have Relic Vault on the table and activate it, the Ancient Relic you selected using Queen Azshara does not cast twice. Apparently Relic Vault works only on regular relics, not ancient ones, even though the ancient relic is still a relic.
A bit of a heads up would have been nice so players do not need to experiment to find out how cards interact.