Fall asleep, restoring 197 health on the first round, 394 health on the second, then 788 health on the third.
While in the Emerald Dream, you cannot swap pets.
Pet Battle: The Emerald Nightmare (Raid)
Pet Battle: [21-22] Sholazar Basin
Drop: Noxious Whelp 
Approximate Drop Rate: 1 in 1,100