Infused Etherwyrm
Drops from Etherwyrm Cage. Infused etherwyrms can be used as portable anima batteries, but they must be trained not to flee at the sight of combat. Flying type. this can only be completed during the Night Fae assault, but it also requires the assault quest 'A Shady Place' to be active.
The Infused Etherwyrm is a battle pet dropped from the Etherwyrm Cage in The Maw, obtainable only during the Night Fae covenant assault when the specific quest 'A Shady Place' is also active.
Guide awaiting review
Wait for Night Fae Assault
This pet can only be obtained during the Night Fae covenant assault in The Maw. The assault rotates and is not always active, so check when it is next scheduled before heading out.
Confirm 'A Shady Place' Is Active
During the Night Fae assault, up to 4 assault quests are active at a time from a pool of around 10 possible quests. The cage and key are only available when 'A Shady Place' is one of the active quests — if it is not up, the cage will not appear in the Desolate Hollow.
Enter the Rift
Use an 
Unbalanced Riftstone to enter the Rift phase of The Maw while 'A Shady Place' is active. Alternatively, you can access the Rift via a Repaired Riftkey or a 
Collapsing Riftstone, though the availability of the cage may depend on whether 'A Shady Place' is currently active.
Collect the Key
While inside the Rift, find and collect the key from the Elusive Keybinder. You can obtain one key per day.
Exit and Open the Cage
Exit the Rift and use the key on the Etherwyrm Cage in the normal phase of The Maw in the Desolate Hollow to receive the Infused Etherwyrm. Since you can collect one key per day, you can repeat this process up to three times (without turning in 'A Shady Place') to fill all three pet cage slots.
Tips
Night Fae players can use the Mushroom Network (Night Fae Circles) in Ardenweald for a direct portal to the Maw assault area, skipping the normal travel route.
