To give context: in a session which I am playing, a player has opted to play as The Princess class. This class has a move which deems them the owner of a Unicorn, which they must then name and describe with tags given by the character sheet. The GM has deemed that this particular move is too strong, however, stating that Unicorns are far too powerful in Dungeon World for him to allow it into the campaign at this time.
He did, however, offer that the Princess could have another creature. They were given a few choices, however, the GM then stated that the animal chosen would share the character's HP pool, and utilize her stats if they chose to take the move. This has made the player reconsider the option entirely, as it would simply give the GM a secondary target to utilize for destroying the Princess without any real benefits.
Granted, there's now some house-ruling going on here, but I would like to know about how to handle the original move (and maybe, by extension, how it would apply to these changes). How should this move work, exactly? Does the Princess just simply have a Unicorn, with monster codex stats, which follows her around and fights on her behalf? Or is this treated more like a Ranger's Animal Companion? Additionally, how do the tags work in relation to the Princess? Do the Color tag buffs apply directly to the Unicorn, or to the Princess (especially in context for the Luminescent tag, which I don't believe that the Unicorn has the Gentle Touch ability?), or both?
For those who do not have the character sheet, the move is a levels 2–5 Advanced Move, and reads as follows:
You have a Unicorn. Choose one from each list and tell the GM their name.
Temperament: Chatterbox, Vain, Brave, Savage
Build: Towering, Skeletal, Solid, Chubby
Colors: Pastel (+1d4 damage), Dark (add the messy tag when in melee), Luminescent (heal +1d6 with Gentle Touch)
(Note that Gentle Touch is a starting move for the Princess that heals for 1d8 or one disease.)