The ravager pet for the quest "Discovering your Roots" (quest=11520) will not despawn once your leave the area Razorthorn Rise.
https://www.wowhead.com/quest=11520/discovering-your-roots
Comment:
"The pet will stick with you for a while. I was able to get all my roots with only one pet (and therefore only one gland) and have plenty of time to spare. Once you fly out of the area, the pet will despawn (else, follow you on the ground and die or just follow you until you reach the edge of the area)."