I was wondering in my reading.
In my book, "There be treasure there! Aawrgh."
I think, between "there" and "be" there is an omission like "must".
Because if not, i'm not sure about the meaning.
Am I right? or there's an other thing that I don't know.
The simplest explanation is this:
There are many non-standard dialects and variations of English, each with its own set of rules. Fictional characters, like real people, will rarely speak perfect grammatical English.
I call the dialect you quoted "Hollywood Pirate English." The main feature of which is the use of be in place of is, are, and am. Also, you have to sprinkle your diction with plenty of "Arrgh's" and "matey's."
The archtype performance of this dialect was by Wallace Beery as Long John Silver in the 1934 film Treasure Island, but the arrgh was perfected by the British actor Robert Newton playing the same role in the 1950 Disney version of that classic R.L. Stevenson story.