that’s a good catch on your part @CPTcman . and that is a nice pet.
here is a thread for farming Eternal Pets. there is an update for 3.0 later in the thread. this build info increases the chance an Enslaver will drop an Eternal Pet instead of something else, even if it is a small chance. which means a chance for an Eternal Pet other than waiting to finish the Mythic Enslaver Feat.
on a side note, I have been playing for 2+ years, and have only found 2 Eternal Pets so far, and they are not as good as yours. and both are rewards from the Mythic Enslaver Feat.