Nightmare Whelpling
Drops from Ysondre. What's a little corruption between friends? Dragonkin type. For this pet, there is a matching Nightmare Whelpling plushie in the Blizzard Store.
The 
Nightmare Whelpling is a pet that drops from the Dragons of Nightmare encounter in the Emerald Nightmare raid.
Guide awaiting review
Queue for Tormented Guardians LFR
Talk to Archmage Timear in front of Violet Hold in Dalaran to queue for the Tormented Guardians wing of the Emerald Nightmare raid.
Defeat Ysondre
Defeat Ysondre in the Tormented Guardians wing. The Nightmare Whelpling has a chance to drop from this boss.
Use bonus roll for higher chances
You can use a Seal of Broken Fate bonus roll on Ysondre to have another chance at obtaining the Nightmare Whelpling.
Tips
The pet also drops in higher raid difficulties if you have access to them.
