Now, I want to preface my choice with this; I am not a Beastmaster expert. I have only used him a handful on times and didn't do too well with him when I did.
However, when I did use him, much of my success came from using the Pet ability with this guy:
Making him your Pet also makes his already nasty attack even better. It adds 1 melee dice when he attacks and adds another if your Beastmaster is in the same zone as him. That means he could be rolling 5 dice and dealing out Rot conditions! Being a level 2 creature, it'll cost 3 additional mana to make him your Pet when you summon him, putting his total cost at 12. But it is so very worth it. This ability, when used on the Tegu, turns it from an above-average creature into one that your opponent will have to be very cautious around, especially if you give him additional enchantments.
What is your favorite pet? Also, what do you want the next question for the readers to be? Leave your answers and suggestions below, and until next time, I'll see you in the arena!