Let's examine some beneficial techniques involved in this distinct style of rhythm playing.
The right hand is enormously important in acquiring the percussiveness and cleanliness we'll need to execute the following riffs. Make sure the palm of your hand is readily available in choking notes and chords after playing to the most extreme dynamic. Djent riffs are "on or off", in the sense that when we land on a rest, there's literally no noise coming from the guitar. Picking hard is also important as some crucial harmonics are only present when doing so. Achieving a perfect balance of both picking hard while remaining tight and clean is one of the primary challenges. When approaching some of the riffs in the following exercises, keep this in mind and practice until it feels more natural.
There's not much to djent riffing with regards to the left hand except for, again, excessive muting. Finding the right place to flatten your fingers across all 6-strings (between notes, during periods of dead space) is something that takes practice. And with every different guitar or guitar tone, there's a different "sweet spot" to avoid nasty over-tones and feedback.