I've read an old forum regarding the same question and Professor Lydia Greyrose said that there are two requirements needed to get the quest.
1. Being level 35 2. Having completed the quest “One in the Snout” in Mirkholm Keep.
I'm currently level 58 and I've completed the "One in the Snout" quest. I received the pop-up notification that says I have to talk to him, but when I went to Baldur Goldpaws, there was no nor could I press 'x' to interact. Was there something that I missed or are there certain quests I have to finish before I can gain access to the quest? One of my friends told me I have to complete all of Grizzleheim to get the quest. I only followed the storyline so far and didn't even bother doing the side quests, so is it possible that I may have to go back and do all of the side quests too to be able to talk to Baldur? I apologize for the numerous questions, but I am so confused as to what I did wrong.
Make sure you talk to Baldur Goldpaws in Wizard City, Olde Town, across from the Bazaar.
For the level 35 spell, you only need to open up Mirkholm Keep with the quest One in the Snout, which you've done.
For the level 55 spell and level 58 school pet, you must continue through Wintertusk and open up Sudriland with the quest Su Su Sudriland.
Both times, the Baldur that you need is going to be the one in Wizard City, not the one waiting by the ship in Grizzleheim. Go pay a visit to the Bazaar and head down the hill towards Tritan Ave, you should find a new quest waiting for you.