Hi, I just started today and was wondering are we able to buy pets to substitute a current pet if you've placed him on a mission but still require an active pet in your party, I only have one pet just now but I do have an egg too. I hope someone can help cause I need to do this troll quest

Hi, if you check the Adcanced Search(Link), you can search for pets and set the specifics you want(Price range, species, level, etc).
This would probably be your easiest way of finding a pet that you can use in battle while your other pet is on a mission.

To use a pet in battle, it must be at least an Adolescent, or older. Egglings and Hatchlings cannot be used to battle with.
You can also only battle with pets that are at or below your user level. So since you're currently a level 9, you can only battle with pets level 9 or below, until your level increases(It'll increase when your highest level pet levels up).

If it would help, I found this pet on Advanced Search, and bought it, and set it up for you for 1 Gold(Which is the lowest a pet can be priced). If you don't want it though, and would rather look through your other options, you don't have to buy it. ^-^
https://www.sylestia.com/view/pets/?petid=7952340