High Priest's Lightsworn Seeker

High Priest's Lightsworn Seeker is a mount obtained by priests.

Source
This item is a quest reward from The Sunken Vault (quest).

Mount Journal
Once plentiful, only three seekers remain on Azeroth after generations of battling the corruption of the cosmos.

History
On the Broken Shore, a High Priest receives word from Netherlight Temple that the Speaker had visited the temple and was looking for the High Priest. The two priest would eventually meet and the leader of the Conclave would rush back to the order hall.

Arriving at Netherlight Temple, the High Priest found Magni and his brother Brann talking with Betild Deepanvil. When he woke up, Magni started to communicate with Azeroth. One day, she told him of a hidden Titan Vault next to the Maelstrom. He doesn't know what's inside of it but thinks it has something to do with the Light and the High Priest. After explaining the situation, the four of them travel to the vault on a submarine from Azsuna.

Arriving at the vault, Magni opens the main door and they go inside. Together, they reawaken Caretaker WH12-B4NG. WH12-B4NG starts examining the four and after getting to Magni, he recognises him as the Speaker and asks if he is looking for the Seekers. Magni says yes and WH12-B4NG starts release them one by one. However, getting to the last one, they discover that it had fallen to void corruption. Obeying its programming, WH12-B4NG initiates protocol. Waves of titan constructs attack the four but are fortunately defeated. When all is calm again, Betild realises that WH12-B4NG and the vault will soon run out of power, leaving no one to look after the seekers. However, Magni realises why he was sent here. It was only a matter of time before the vault fell. Not wanting the seekers to be lost forever, Azeroth requested that Magni bring the High Priest here to look after them. The Conclave agrees to this request.

Back at Netherlight Temple, the High Priest climbs on top of one of them and makes it his own.