What is the point of this line in the Hide of the Feral Guardian? [closed]

Question

The Hide of the Feral Guardian, a legendary item from the Explorer's Guide to Wildemount, includes the following ability.

When you cast the polymorph spell using this armor, you can transform into a cave bear (use the polar bear statistics).

Why does it mention both bears, and not just turn the user into either a polar bear or cave bear through the polymorph spell? At first I thought it might be because of the book each creature was from, but they both have stat blocks in the monster manual, and neither are in the explorer's guide elsewhere as far as I can see.

Effectively, why does the magic item tell you to use one bear with the statistics of another bear when you polymorph, instead of just saying "When you cast the polymorph spell using this armor, you can transform into a cave bear" or "When you cast the polymorph spell using this armor, you can transform into a polar bear".

Answer 1

The Cave Bear is a variant of the Polar Bear

While in online sources like D&D Beyond both cave and polar bears appear separately, in the Monster Manual (page 334) the cave bear appears only as a variant description under the polar bear entry; they use the same stat block with the only suggested change the addition of darkvision. By convention source books do not reprint creatures from the Monster Manual unless they are beginner products intended to be used independently, and to accurately direct readers to the appropriate entry it references the polar bear. (Neither appear in the table of contents as they are listed in Appendix A, Miscellaneous Creatures.)

In addition, the free Basic Rules do not list the cave bear variant, as the shorter monsters section in that document lists stat blocks only. A player with only the Basic Rules for monster information can still use this book, though whether that’s part of the reasoning is speculation.

As for using the spell polymorph rather than “directly” transforming the wearer, the item is a “Vestige of Divergence”, a type of item used by Matt Mercer in Critical Role which grows more powerful over time. The cave bear form is only available when the armour is “awakened”, and is an improvement to the original transformation from its “dormant” state:

As an action, you can use the armor to cast polymorph on yourself, transforming into a giant owl while retaining your Intelligence, Wisdom, and Charisma scores. This property can’t be used again until the next dawn.

Answer 2

That line only makes sense in the context of previous lines.

The Hide of the Feral Guardian is a Vestige of a Divergence, a special magical item that can unlock better versions of its bonuses by overcoming challenges. That line is part of the Hide of the Feral Guardian's second stage. If you read the first stage bonuses, its meaning becomes clear:

Hide of the Feral Guardian (Dormant)
While you wear the armor in its dormant state, you gain the following benefits:
...
As an action, you can use the armor to cast polymorph on yourself, transforming into a giant owl while retaining your Intelligence, Wisdom, and Charisma scores. This property can't be used again until the next dawn.

The second (Awakened) stage of the Hide of the Feral Guardian includes the line you are asking about, and now that we have read the first (Dormant) stage, it should be clear that that line is modifying the polymorph ability gained in the first stage. Once the Hide reaches the second stage, the wearer can choose the giant owl or cave bear (polar bear) statistics when using the armor's polymorph ability, rather than being limited to only the giant owl.

TLDR: That line does not mean "when you cast the polymorph spell while wearing this armor", it means "when you use this armor's magical ability to cast the polymorph spell for you, which comes with a limited selection of forms".