Zephyrians
The people of Ether. What sustained them was not a god or a craft they invented but the realm itself — the Heart of Ether, showing through the Burning Tree. The Tree gave, and they received.
Their own working, the transfer craft the Gift is written in, is the same motion turned outward: giving what you hold to someone who does not hold it. The verse of it reads half-familiar to a Zephyrian, a cadence from home rather than a spell learned.
Of Minds
Taara is a Zephyrian of Minds.
What became of them
Ether froze. The Cold-Sigils were placed on the Burning Tree.
What survives of them outside Taara is a single orb in Morgantha's Memory Vault — hundreds of Zephyrian memory-fragments compressed together. Not individuals. The collective warmth of what Ether used to feel like, the hum of the Burning Tree, the pulse of her kin, catalogued and filed as one stolen keepsake.
Strahd
He knew them, and spoke in session 14 as though their history was significant — "I have not seen a Zephyrian in a very long time."