# Is a Duergar's Expansion and Invisibility abilities spell-like or psi-like? And does it matter?

The Duergar in the Monster Manual says that their expansion and invisibility abilities are spell-like abilities. But in the Expanded Psionics Handbook they are psi-like abilities.

Which is it? And does it matter? For example, if there was an area effect spell that prevented spell-like abilities, would it effect a duergar's abilities (assuming they were psi-like)?

RAW answers please, though failing that I'm open to well reasoned opinion.

• As a side note, the raw tag is not meant to be used on questions looking for raw answers. – ammut Apr 28 '19 at 8:45
• What's it meant to be used for @ammut? – NeomerArcana Apr 28 '19 at 9:16
• @NeomerArcana We have decided to not use it at all. See this meta discussion. – Someone_Evil Apr 28 '19 at 9:32
• Yeah @Someone_Evil I just saw that. Didn't realise it was contentious – NeomerArcana Apr 28 '19 at 9:33

It is either.

Chapter about playable races tells us to see chapter on monsters to see how psi-like abilities work. A box on the bottom of page 184 in monster chapter says that creatures in the XPH are psionic versions of regular ones*. Thus, you can use whichever you choose to.

The way we dealt with this when we were playing / I was DM in a club was to decide up front if campaign or adventure was using psionic or not, and then we were using psi or regular versions exclusively. Mixing them didn't sound like a good idea, but admittedly we never found any rule preventing that.

Exact nature of the ability does not matter by default. Page 55 of Expanded Psionic Handbook defines psionic-magic transparency as default rule. If that's the way you play, effects that affect spells and spell like abilities works just as well on powers and psi-like abilities. Of course, there is a "psionic is different" option that would make it matter. In that case, I strongly suggest using only psionic variants of races and monsters that have such variants, because mixing them becomes extremely confusing for players.

* If you want to nitpick, it only says so about creatures in monster chapter, but there is nothing about that matter in the playable races chapter, so this seems to be pretty reasonable extrapolation.

• @KRyan answer expanded – Mołot Apr 28 '19 at 13:19

As indicated in this answer, it can be either. However, there is one substantial difference in how they play out: because psi-like abilities are manifested as if a number of power points equal to the user's manifester level had been spent, a duergar of sufficiently high level can take advantage of the expansion power's augmentation options.

While the difference for low-level duergar isn't that meaningful (2 minutes/HD duration for enlarge person vs 10 minutes/HD for expansion), a 7HD duergar can grow two size categories (dropping the duration down to 1 round/HD until they get to 9HD and can use both augmentation options), which can give the psionic duergar a nontrivial edge vs. the magical one.

On the other hand, there are some cases (e.g. dispel magic) where the magical duergar's caster level of twice their HD (minimum 3) can give them an edge over the psionic duergar's manifester level of their HD (minimum 3).

Which one of those is more powerful (or whether the differences are relevant at all) will depend on the specific campaign.