Assume Supernatural Ability is a feat that allows a shape-shifted creature to use an ability of its adopted form:

You learn to use a single supernatural ability of another kind of creature while assuming its form through a polymorph self spell or a similar effect.

It's clear how this interacts with abilities that require actions to be used. However, how does it work when I want to assume a passive ability? I've been looking at the nymph's Unearthly Grace (Su) which passively grants bonuses to AC and attack. I'm a doppelganger, so I would assume this is permitted.

Additionally, the feat bestows penalties when the user activates the ability he is emulating:

Using this alien ability is disorienting. You take a -2 penalty on all attack rolls, saving throws, skill checks, and ability checks. Additionally, in a stressful or demanding situation (such as combat), you must succeed on a Will save (DC 19) or be unable to use the ability.

Do I suffer these penalties when attacked, entering combat, or am I always suffering penalties as long as I'm shifted into a nymph?

  • \$\begingroup\$ A doppelganger's Change Shape ability is more like a disguise self spell than a polymorph spell. They don't gain any of the physical characteristics, so I'm not sure they are eligible for the feat. Aside from that, what penalties are you referring to? \$\endgroup\$ Jun 15, 2016 at 16:31
  • \$\begingroup\$ @gaynorvader It's a spell. I forget the feat, but there are upgrades for spell-like abilities to supernatural, which is what doppelganger has, a supernatural ability, which would make it a magical change. This is the only requirement for the feat. It is not like disguise self in that it cannot be removed or countered magically and I can cast it at will. \$\endgroup\$ Jun 15, 2016 at 17:13
  • \$\begingroup\$ @gaynorvader also,note, alter self, which is similar to the doppelganger su, is transmutation whereas disguise self is illusion. I don't think an illusion would work, but I am physically altered, which is why you do a sense motive against a doppelganger, not a spot while they are disguised. \$\endgroup\$ Jun 15, 2016 at 18:07
  • \$\begingroup\$ Supernatural Transformation feat is the feat I was thinking of that turns a spell-like ability into a Supernatural Ability. \$\endgroup\$ Jun 16, 2016 at 2:43
  • \$\begingroup\$ The typical doppelganger can't use the supernatural ability change shape to assume the form of a nymph; a nymph's type is fey while the special ability change shape is limited to a "Small or Medium humanoid." (Still a darn good question, though.) \$\endgroup\$ Jun 16, 2016 at 12:42

2 Answers 2


Assume Supernatural Ability

A general feat (Savage Species p.30) available to be taken by any creature with the requisite Wisdom Score, and an "ability to assume a new form magically," Assume Supernatural Ability is contentious in its interpretation. This is partly because form altering magic or abilities have been fraught with difficulty, and partly because the feat is not descriptive, and gives no examples for clarity.

The Problem with Polymorph

Because Savage Species was published almost four months prior to the completion and release of the 3.5 Revision of Dungeons & Dragons in 2003, and had been in development throughout most of the time of the revision, it has intermediate rules information between the 3rd and 3.5 versions of the game.

Many creatures in 3.0 had polymorph self as a spell-like ability (Sp), while others had different, usually supernatural (Su) abilities, such as Polymorph, Change Shape, Alternate Form, or Alter Self, each of which often mimicked polymorph self, but also alter self or shapechange. With the 3.5 Revision, the polymorph self spell became the polymorph spell, and almost every instance of it, alter self, and shapechange was removed from creatures' lists of abilities. Instead they often became the precursors of the current Change Shape and Alternate Form abilities. Even then, there were multiple changes to polymorph, Change Shape, and Alternate Form until the designers eventually appeared to give up and make the 'Polymorph' sub-school, which they revised at least once more until producing the 4th edition.

For example, in 3.0, Doppelgangers had alter self as a (Su) ability at will, Avolakia (from Monster Manual 2) had (Sp) polymorph self (humanoid form only) at-will, Succubi had the same (Sp) as Avolakia, Grimalkin (MM2, p122) had (Su) Polymorph (as polymorph, into Medium or smaller animals, beasts (revised to animals, usually) and vermin), Imps had (Su) Polymorph (as polymorph, 1-2 forms, Medium or smaller), Quasits had (Su) Alternate Form (also as polymorph, 1-2 forms, Med. or smaller), and the Phasm had (Su) Alternate Form (as shapechange, Diminutive-Large).

Each of these creatures got either a form of Change Shape or Alternate Form, except the Phasm, which got its Alternate Form switched from the more powerful shapechange to polymorph. This seems to indicate to me that nearly all form altering abilities are 'similar' to polymorph.

Interactions between 3rd and 3.5 form altering abilities are, therefore, to put it in technical terms, an awful mess. This highlights why some players will say that most form altering magic that lets a creature appear to be another to meet the 'polymorph selfspell or a similar effect' metric of the Assume Supernatural Ability feat, and others adhere to only converting the words polymorph self to polymorph.

Vague Wording is Vague

Another reason that the feat's use is contested is that the benefit is nebulously worded, stating:

"You learn to use a single supernatural ability of another kind of creature while assuming its form through a polymorph self spell or a similar effect..."

The first sticking point is the '...a single supernatural ability of another kind of creature...' clause. The ways that this can be read are usually:

'choose one (Su) ability of a creature whose form you can assume, when you assume its form, you may use that ability'


'choose one type of (Su) ability that creatures have, when you assume the form of a creature that has an ability of the same name, you may use that ability'


'when you take the form of a creature, you may use any one (Su) ability that kind of creature normally has'.

The second sticking point is the '...while assuming its form...' clause. The taking of form is not strongly defined, with players debating how weighted the word 'form' is within the rules. Even the supposedly 'weak' shape altering magic of Eberron's Changeling, Minor Change Shape, is assumed to allow the changeling to take the form of a humanoid, as evidenced by the Racial Emulation feat (Races of Eberron, pp.110-111)

"...When you use your minor change shape ability to assume the form of a humanoid creature..."

Thus, the answer to the question of whether a Doppelganger can qualify for and use Assume Supernatural Ability is very difficult to definitively answer, but I personally would say 'yes'. Ultimately, the players, including the DM, of course, must decide whether to allow it.

In hopes of balance, I'd probably just add in a clause that only if your HD or Character Level are equal to or greater than that of the creature you're appearing as are you able to assume that creature's form, exactly as with form altering spells in 3.5 rules.

Finally, an Answer!

Regarding the last part of the Benefits section of the feat:

"...Using this alien ability is disorienting. You take a -2 penalty on all attack rolls, saving throws, skill checks, and ability checks. Additionally, in a stressful or demanding situation (such as combat), you must succeed on a Will save (DC 19) or be unable to use the ability."

This is a holdover from the 3.0 edition of polymorph other, which polymorph self inherits from. It has a very similar clause, which states (PHB 3.0, pp.236-237):

"...The new form can be very disorienting. Any time the polymorphed creature is in a stressful or demanding situation (such as combat), the creature must succeed at a Will save (DC 19) or suffer a -2 penalty on all attack rolls, saves, skill checks, and ability checks until the situation passes..."

The feat looks to actually state that you're 'disoriented' (with the same penalties as being 'shaken', by the way...) the whole time you're using the creature's ability. Thus if it's an attack, during the attack action, you take the penalty. If it's a constant (Su) defense or ability, you're always disoriented. Additionally, you must make the save or either lose, or be unable to use, the ability in a clinch.

That's why Improved Assume Supernatural Ability is in the same book. It has a higher Wisdom prerequisite, but states (Savage Species, pp.35-36):

"...This feat functions like Assume Supernatural Ability, except that you do not take the -2 penalty on all attack rolls, saves, skill checks, and ability checks when using it..."

Happy Gaming!

  • \$\begingroup\$ So “this ability” refers to Assume Supernatural Ability itself, rather than the supernatural ability you’ve assumed? Gee, I wonder why that was unclear :P Great find. \$\endgroup\$
    – KRyan
    Aug 21, 2016 at 14:27
  • \$\begingroup\$ The thing that clarified it for me is polymorph other with which you took the penalty while in the alien form. With this feat, you take the penalty while using the alien ability. Rather than save, you instead become 'disoriented' automatically, and in combat need to make the save or be unable to use it, which would negate the automatic disorientation. With the update to polymorph, only while using the ability do you suffer the disorientation, as being polymorphed no longer disorients the target. The save, however, is always required, even with Imp. Assume Su. Abil. \$\endgroup\$
    – Chemus
    Aug 21, 2016 at 18:57

The Doppelganger's Change Shape (Su) ability says:

A doppelganger can assume the shape of any Small or Medium humanoid. In humanoid form, the doppelganger loses its natural attacks. A doppelganger can remain in its humanoid form until it chooses to assume a new one. A change in form cannot be dispelled, but a doppelganger reverts to its natural form when killed. A true seeing spell or ability reveals its natural form.

Compare the Polymorph which says (among others):

The subject gains the Strength, Dexterity, and Constitution scores of the new form but retains its own Intelligence, Wisdom, and Charisma scores.

It also gains all extraordinary special attacks possessed by the form but does not gain the extraordinary special qualities possessed by the new form or any supernatural or spell-like abilities.

I would contend that as intended the Doppelganger's Change Shape ability is NOT similar, because it does NOT grant the physical ability score NOR the extraordinary special attacks of the assumed form.

Given the feat:

You learn to use a single supernatural ability of another kind of creature while assuming its form through a polymorph self spell or a similar effect.

And the feat's pre-requisite:

ability to assume a new form magically

I would therefore contend that the Doppelganger cannot gain the benefit of this feat.

Still, let's imagine that either the GM allows it or you use Polymorph Self or a similar effect.

The feat mentions:

Using this alien ability is disorienting. You take a -2 penalty on all attack rolls, saving throws, skill checks, and ability checks.

There is:

  • no mention of the trigger
  • no mention of the duration

For an ability usable as a Standard Action, and with an instantaneous effect, the lack of duration is quite troubling. There is little penalty if this only lasts for the duration of the action, since you do nothing else then.

So? Nothing.

The book is silent. I seem to remember that Savage Species is not exactly the most friendly book in that regard.

Let's house rule!

I would personally NOT allow this feat to be taken by a Doppelganger.

Unearthly Grace (Su)

A nymph adds her Charisma modifier as a bonus on all her saving throws, and as a deflection bonus to her Armor Class. (The statistics block already reflects these bonuses).

This is much stronger than any feat.

The Paladin, at level 2, gains Divine Grace (Su) which only covers the saving throws portion; and the Paladin is a MAD character.

The Battledancer, at level 1, gets to add its Charisma to AC, but only when unarmored. And it's melee class (they need all the help they can get).

The ability to your Charisma modifier to both saving throws and AC (on top of regular armor) at all times is worth much more than the cost of a single feat.

It's somewhat broken with Polymorph, as it forces you to cast the spell and maintain it, and by the time you can extend it sufficiently or persist it it has lost much appeal. Without the Polymorph restriction, however, it is completely broken.

  • \$\begingroup\$ Alter self does not need to be similar to polymorph, just "magically caused", which a supernatural ability is. As it is a transmutation, and not an illusion, I am ACTUALLY changing so based strictly on what it states it would be permitted. I know it sounds broken, but my doppelganger kinda sucks and needs AC. The DM has stated it would be permitted, but I wasn't certain how to play the passive abilities since there's no activation. \$\endgroup\$ Jun 16, 2016 at 12:44
  • \$\begingroup\$ Assume Supernatural Ability is one of the quickest ways to break the game into itty bitty pieces, and is used in a lot of theoretical-optimization tricks. \$\endgroup\$
    – KRyan
    Jun 16, 2016 at 13:00
  • \$\begingroup\$ @NationWidePants: The feat text says Polymorph self or similar effects, so per the rule it would probably not be allowed; however it is indeed within your DM purview to house-rule, if (s)he determines this is better for the game. In your stead though, I would actually ask a question posting your character statistics and asking how to improve its survivability, there are really good players on this "board" (notably KRyan, who just commented above) and they could probably help you. \$\endgroup\$ Jun 16, 2016 at 13:23
  • \$\begingroup\$ @KRyan: I would be interested on your reading of the trigger/duration of the penalty mentioned by the feat. It seems really incredibly vague to me. \$\endgroup\$ Jun 16, 2016 at 13:24
  • \$\begingroup\$ @MatthieuM. It is, and I agree with your answer. I do not see any clear way to determine what the feat is supposed to do with any certainty. \$\endgroup\$
    – KRyan
    Jun 16, 2016 at 13:25

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