David the Destroyer

 Do you think david being paradise's sole ihabitant has some how exterminated all the engineers or more likley turn them into test subjects.

If he has a hand in unleashing a new kind monster in Covenant, that is likely the white back/head burster critters. They most likely are the product of black goo unleashed on the Engineers.

Obviously David had to ninja that one spectacularly. Sneak it in a water source, or aerosolize it. Do it on the down low.