Source: Cult of Cinders, pg(s). 81
Bidas magically pose as humanoids to infiltrate settlements, preferably those that control gold or coal mines which they can live in. Over weeks or months, they establish their importance in the settlement, until they become ready to reveal their terrible price: regular offerings of flesh and gold. The bida then moves to its lair and hides the settlement from the outside world by concealing it in an illusion and demanding the residents to destroy any roads connecting to it, as it grows fat from regular sacrifices.
Bidas prefer the company of delicious food and only reluctantly tolerate other bidas. In rare cases, two bidas might conquer a settlement together, exploiting more wealth and food from the populace. Like most dragons, bidas are fond of treasure and gather vast hoards, usually from those whom they have cowed into submission.