What are the mechanical differences between the Shapechanger and Change Shape abilities?

Question

Many creatures can transform into other forms. For some, the ability is called "Shapechanger".

Doppelganger: Shapechanger. The doppelganger can use its action to polymorph into a Small or Medium humanoid it has seen, or back into its true form.
Jackalwere: Shapechanger. The jackalwere can use its action to polymorph into a specific Medium human or a jackal-humanoid hybrid, or back into its true form (that of a Small jackal).
Succubus: Shapechanger. The fiend can use its action to polymorph into a Small or Medium humanoid, or back into its true form.

Meanwhile, other creatures have a very similar "Change Shape" ability:

Deva: Change Shape. The deva magically polymorphs into a humanoid or beast that has a challenge rating equal to or less than its own, or back into its true form.
Night Hag: Change Shape. The hag magically polymorphs into a Small or Medium female humanoid, or back into her true form.
Oni: Change Shape. The oni magically polymorphs into a Small or Medium humanoid, into a Large giant, or back into its true form.

I'm not sure why there are two terms for abilities that appear nearly identical.

What are the mechanical differences (if any) between the "Shapechanger" and "Change Shape" abilities?

@Guill It is a long-established practice and even policy that asking about designer intent is off-topic. Searching the site, you can find countless questions closed for this reason. Of course, if you want to open a Meta feel free to do so, but know that current site practice is very much to close designer intent questions. In fact, the [tag:designer-reasons] tag states: "OFF TOPIC". I understand that votes years later may have moved answers around, but our policies and practices do not change vote-by-vote. A revisit of some kind would be necessary — Exempt-Medic, Sep 28 '21 at 11:16
@GuillaumeF. you could rephrase the question like "what are the mechanical difference between Shapechanger and Change Shape" in order to make it answerable. — enkryptor, Sep 28 '21 at 11:18
Questions like "Is there a reason why this thing is called X" have the obvious answer "because the game devs named it X". We are not the devs so we don't know why exactly. That's why these questions are off-topic. — enkryptor, Sep 28 '21 at 11:21
somewhat related (see the accepted answer): Can I true polymorph into an Ancient Brass Dragon, and then use its Change Shape ability? — PixelMaster, Sep 28 '21 at 14:56

enkryptor · Accepted Answer · 2021-09-28T15:46:00.830

The action is named after the creature subtype

Monsters with the Shapechanger action have the creature subtype "Shapechanger".

Doppelganger is a "monstrosity (shapechanger)"
Jackalwere is a "humanoid (shapechanger)"
Succubus is a "fiend (shapechanger)"

This is important because some spells and magic effects work differently with shapechangers.

Creatures with the Change Shape action usually are not shapechangers:

Deva is a "celestial"
Night Hag is a "fiend"
Oni is a "giant"

The action itself has a different name, and its description might vary (see below).

Shapechanger are nearly identical for all shapechangers:

...can use its action to polymorph into a Small or Medium humanoid it has seen, or back into its true form. Its statistics, other than its size, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

The Change Shape description varies depending on the creature (emphasis mine):

The deva magically polymorphs into a humanoid or beast that has a challenge rating equal to or less than its own, or back into its true form. It reverts to its true form if it dies. Any equipment it is wearing or carrying is absorbed or borne by the new form

The hag magically polymorphs into a Small or Medium female humanoid, or back into her true form. Her statistics are the same in each form. Any equipment she is wearing or carrying isn't transformed. She reverts to her true form if she dies.

It also explicitly says it is "magical", hence, can be detected by the Detect Magic spell. See Is the changeling's Shapechange ability detectable with Detect Magic?

Are the actions really identical? At a quick glance, one says magical and the other doesn't. — Ryan C. Thompson, Sep 28 '21 at 14:29
Note, not all creatures with the Shapechanger ability also have the tag, for example, the imp — Exempt-Medic, Sep 28 '21 at 15:07
@Medix2 I guess it's because it already has a devil subtype. But this does not really matter, I guess. In some cases the rules fall short. The writers can miss details, they are only humans after all. — enkryptor, Sep 28 '21 at 15:44
@enkryptor Meanwhile the Quasit apparently has both the demon and shapechanger tags. I agree, it could totally just be human error though — Exempt-Medic, Sep 28 '21 at 15:52
@Medix2 yeah, it looks like the Imp should have the shapechanger tag, but apparently it hasn't. — enkryptor, Sep 28 '21 at 15:54

Exempt-Medic · Answer 2 · 2021-09-28T15:14:01.427

Some features and effects specifically impact Shapechangers

For examples of such features there are the moonbeam and polymorph spells:

A shapechanger makes its saving throw with disadvantage. If it fails, it also instantly reverts to its original form and can’t assume a different form until it leaves the spell’s light.

The spell has no effect on a shapechanger or a creature with 0 hit points.

These spells have effects specifically against shapechangers, though it's worth noting that Shapechanger is a monster tag and having the Shapechanger ability does not guarantee a monster has the tag, nor does having the Change Shape ability guarantee a monster doesn't have the tag. That said, I have found very few exceptions to this trend, notably the Imp has the Shapechanger ability but not the trait.

Change Shape is usually magical and Shapechanger is not

The features themselves do have one notable difference: Change Shape is (usually) magical. The Change Shape feature, usually, includes the phrase "magically polymorphs" which tells us that the feature is magical and thus can be detected by things like detect magic or stopped by things like an antimagic field. Note, not all instances of Change Shape are explicitly magical, for example the Gingwatzim and the Jiangshi.

The "usually" reminds me of a relevant point: there are no general rules for these features, so just because two different monsters both have an ability with the same name doesn't mean those two abilities have anything to do with each other. They're all meant to be self-contained. — Ryan C. Thompson, Sep 28 '21 at 21:15

What are the mechanical differences between the Shapechanger and Change Shape abilities?

2 Answers2

The action is named after the creature subtype

Some features and effects specifically impact Shapechangers

Change Shape is usually magical and Shapechanger is not

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