Perhaps you will be interested
You need to complete the following achievements:
Ragnaros, Watch and Learn
Murlocs, Harpies, and Wolvar, Oh My!
Best of the Beasts
Master of Magic
The Lil' Necromancer
You will receive Nightmare Treant pet
Here you can buy Family Familiar achievement for EU or US Servers.
You'll get guide for completing Family Familiar achievement