How to Handle Daemonhosts in Darktide
What you need to know about the Daemonhost boss in Warhammer 40K: Darktide
Daemonhosts are unlike other bosses in Darktide because they are optional encounters. They are an ambient enemy, meaning they will not "spawn in" to attack the player like other bosses, but will be waiting at a random place in the level. You often hear them before you see them, as they will whisper to themselves insanely due to the daemonic possession that they are struggling with.
Avoid Daemonhosts if Possible
Daemonhosts are extremely dangerous and can be ruinous for your party, but 99% of the time you can avoid fighting them entirely.
They begin in a passive state, kneeling down on the ground, but if someone provokes them by firing a weapon near them, sprinting or going too close, they will switch to an "angry" state, signaled by standing up and shouting much more aggressive voice lines.
If they are provoked again while in the angry state, they will become hostile and begin attacking the player that provoked them. Hitting them with any attack may cause them to switch straight from passive to hostile.
In combat, the Daemonhost will attack the same player relentlessly with rapid hits that drain lots of stamina and are hard to dodge. When the player is downed, they will drain the life out them. If the boss is not killed before this process is completed, then the victim will be put out of action and have to be rescued later in the level. There is no other way to interrupt this.
The Daemonhost will then choose a second player and do the same thing to them. The Daemonhost will switch to the player who is closest to them when the first player has died.
If it is still alive after killing two players, the Daemonhost will usually flee combat. This means that Daemonhosts often don't cause a party wipe on their own, but putting two players out of action leaves you very vulnerable to any further mishaps, and it's generally best to simply avoid fighting them at all.
How to Fight the Daemonhost
If you decide to fight the Daemonhost, the best way of dealing with it is to have an Ogryn with the Battle Maul & Slab Shield weapon equipped. They should be the one to make the first attack against the Daemonhost in order to get the attention of the boss.
If the daemonhost was pulled by accident, then make sure the Ogryn stays close to the Daemonhost in order to get the aggro if the first player dies before the boss does.
The Ogryn can use the special ability of this weapon, called Defensive Stance, where he slams the shield to the ground, allowing him to block attacks without using any stamina. The Ogryn is immobile while doing this, so other party members need to deal with specials quickly so the Ogryn can continue tanking the Daemonhost undisturbed.
If you don't have an Ogryn with this weapon in your group then you will have a much harder time fighting the Daemonhost - in this case the player being attacked should try to play as defensively as possible, using dodge, block, line of sight and elevation changes where possible to get some reprieve from the attacks of the boss, while the rest of the team focus on killing the boss as fast as possible. But if they are too slow then there will almost certainly be casualties, which is why avoiding them altogether is really the best course of action.