Throld's Comments

I will say this about Baa'l. If the interaction with Uuna doesn't trigger, then you need someone to use the Gastropod toy from the Thunder King raid to "kill" Baa'l.

The Gastropod user needs to only do this once. If you kill Baa'l with Jerry during Uuna's interaction with him, it will re-bug him, and he won't get reduced to a defeatable pet, as the effect on Baa'l takes a few extra seconds to work.

The rare this drops from is located on the 2nd level of Tol'Gar Mythic

As you enter the 2nd level, open the prison cell doors on the right side (rogue, skeleton key, scroll of unlocking etc), and enter the passage at the back of the pair of joined cells. The rare is at the end of the tunnel. Kill the slime to get the pet, loot is personal, so it will be random as to who gets the pet.