Daemon Brutes or Ruinstorm Daemons are your generic lesser daemons born from Chaos itself and serve no God.
These hulking creatures of twisted muscle and sharpened bone act as the vanguard of the Daemonic horde, breaking the fragile ranks of mortal armies and serve as a bulwark for the smaller minions of Chaos that follow in their wake. Each of these monsters towers over even Space Marines and are capable of shrugging aside Bolter shells as if they were Flashlights.
As they are not aligned to any of the four Chaos Gods, these creatures, like their more dimwitted Chaos Beast, are neutral in the Great Game. Compared to the limp-dicked Furies with which no one wants to have any association, Daemon Brutes provide as useful bodyguards with no pre-set agendas so long as they can reliably Rip and Tear, which you'd think would make them Khornate by default, but whatevs.
These guys only appear in the Horus Heresy under the Daemons of the Ruinstorm codex. Daemon Brutes are the elite units. While not quite as strong as a Greater Daemon, these guys are still plenty strong for Infantry and possess three wounds each. In addition, you can buy up to three of these guys to act as a bodyguard for your footslogging Daemon Lord, giving a massive wall of bodies. Can guarantee to materialize in the mortal realm on the first turn. They can have up to two Emanation options.
The auto arrive turn one cannot be overstated enough. In an army where you will pretty much be deploying nothing on the board, these guys stop you losing turn one right off the bat due to bad dice rolls or oppression from afar. Give them the 3+ right away, just do it. These guys are basically Castellax when they arrive just without the guns, so taking a couple of units of these with a 3+ and rending gives you some really durable units turn one that can crump mortals pretty reliably. Other emanations are good, but you really want that armour save if you can, otherwise you're at the mercy of autocannons and heavy bolters which are a lot more common than you think.