But those aren't languages. Those are cyphers. Thieves Can't is a cypher of another spoken language.Except that yes there is. The DM just has to make it up. The spell comprehend languages very specifically doesn't decode secret messages in a cypher.
"This spell doesn't decode secret messages in a text or a glyph, such as an arcane sigil, that isn't part of a written language."
Natural language doesn't come into being with cyphers being needed, but an artificially created one used by the BBEG and his lieutenants would. The PHB also does in fact have secret languages that can only be understood by those who speak it. Thieves' Cant(PHB page 96). Unlike the secret druidic language which explicitly says that it can be understood by magic, there is no such provision in Thieves' Cant.
The DMG also mentions creating new languages(including secret languages) on page 20, Dark Speech in the Book of Vile Darkness, and mentions languages so alien that they threaten to break a character's mind on page 263.
Which is the issue ..
...of why there is 1 page of languages, 1 spell that defeats them all, and less in the DMG to how to defeat the spell with no real examples.does anyone else think that comprehend languages is too powerful/useful for being a first level spell? given that it manages to obviliate a large section of a kind of obstacle, is it a convenience that we've just come to expect having?
And that's as much as I can say on this in a + thread.