Retains its original name after taming. To find this pet, you first need to reach renown 9 with Loamm Niffen so that you gain "Myrrit Affinity". Once you've done so, there's a chance than you can spawn Treasurewhiskers during a Sniffenseek dig (possibly any dig, but that hasn't been confirmed). In the dig cave, command Myrrit to use his Sniff ability. If he detects an unusual patch of scent, you can burrow and uncover it, possibly revealing Treasurewhiskers. As this mouse can spawn as either purple or gold there's a chance you may not get the colour you desire first time.
Level scaling: Most NPCs will scale with the Hunter's level, within the constraints of their level range. Hunters can tame regular NPCs up to 2 levels higher than them, but can only tame elite NPCs of the hunter's level or below.