Can the Balhannoth speak?

Question

From Mordenkainen's Tome of Foes comes the Balhannoth (p. 119). In the Languages part of its statblock, it says:

Languages understands Deep Speech, telepathy 1 mile

Normally when a creature speaks a language it would say just "Deep Speech". When it can understand it but cannot speak it, it would say "Understands Deep Speech, but can't speak" or "Understands Deep Speech, but doesn't speak" (which, effectively is kind of the same thing I'm assuming).

Now in this case it only says "understands". I have a gut feeling that this creature can't speak. Can anyone here confirm this somehow?

Answer 1

It can understand but cannot speak

In the rules for Monster Languages there is a clear distinction between understanding and speaking a language:

Sometimes a monster can understand a language but can't speak it, and this is noted in its entry. A "--" indicates that a creature neither speaks nor understands any language.

This distinction is also made in Tongues and Thieves' Cant.

You are right, the vast majority of instances read "understands X but cannot speak," but this is redundant and should never have been written in the rules. It serves only to cause confusion in edge cases such as the one you found.

However, it can communicate telepathically.

Answer 2

Yes, but only telepathically

The Balhannoth can't physically speak Deep Speech, or any other language for that matter, because as you state, it can only understand it. However, it doesn't have to speak any languages physically to communicate effectively, because it is also telepathic, for which the Monster Manual states:

Telepathy Telepathy is a magical ability that allows a monster to communicate mentally with another creature within a specified range. The contacted creature doesn't need to share a language with the monster to communicate in this way with it, but it must be able to understand at least one language. A creature without telepathy can receive and respond to telepathic messages but can't initiate or terminate a telepathic conversation.

So the Balhannoth can communicate telepathically with other creatures. I personally assume that the 'Understands Deep Speech' was added primarily to satisfy the "must be able to understand at least one language" requirement of Telepathy, else two Balhannoths would not, RAW, be able to communicate.

Answer 3

The Balhannoth was first introduced in Monster Manual IV for D&D 3.5. In that edition, it had no known languages at all.

While its abilities have changed between versions, I suspect that they didn't intend for it to gain speech.