It is a freebie spell you can choose from at lvl 20. This is a really good spell to get IMO if you are non-twinked since it is a tank pet and adept 2 quality. However if you got plenty of gold to spend you might pick a different adept 2 freebie spell at lvl 20 and just wait till lvl 24 when you get the soldier pet and upgrade it to adept 3.
At level 30 you can choose a Adept 2 fire pet, but to be honest Id get a different spell cause its not good for nothing. I found my tank pet does just about the same DPS as the fire pet, and it can tank a whole lot better.
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Hi