The Quackcestor
Source: Pet Battle. This is not your grandfather's duck! Or.. maybe it is? Undead type. Head to and find a Centaur hut with clickable at Interacting will apply a 1-hour buff on you to enable seeing residual spirit elements in the .
The Quackcestor is a wild pet found in the Ohn'ahran Plains during Dragonflight that requires a special buff to even see, making it one of the more involved critter captures in the expansion.
Guide awaiting review
Grab the Essence Buff
Head to a Centaur hut at 85.71, 20.73 in Ohn'ahran Plains and interact with the object inside — it looks like a chemistry set on your left as you enter. This grants you the 
Essence of Awakening buff, which lasts 1 hour and allows you to see The Quackcestor in the Primordial Vale area. If you die, the buff is removed, but the object is clickable again after a few seconds.
Capture Your Duck
Fly to the spawn area at 42, 45 in Ohn'ahran Plains — The Quackcestor appears as a wild pet battle with two critter companions: a Pricklefury Hare and a Treeflitter. It spawns as a rare and respawns very quickly, so circle the area and re-engage spawns until a rare quality one appears. Note that the Essence of Awakening buff only needs to be active when you engage the battle — if it expires mid-fight, you will still receive the pet upon capture.
