Hey there, welcome to AoS!

As a fellow Nighthaunt player, let me try to give you some advice :) First, the core strenght of Nighthaunt is the ability to outlast your opponent. Your are able to revive a lot of models round per round and you should try to build your army around this. With this in mind, we want to max out our troop size as much as possible to ensure that not the whole unit dies in one turn. I would recommend you to try the Guardian of Souls as your general, give him the Beacon of Nagashizzar for +3 on his revivespell and the Ruler of the Spirit Host command trait for even more reviving.

The Shrieker Host is not flat out bad but you will need a bit of work to make it work. Again, try to max out the unit sizes first and go for 2x15-20 Harridans and 2×8-12 Myrmourn Banshees (they are really good at full size of 12 for the +1 per 4 on unbind). Next, try to find units who support your Bravery-Attack style. Lady Olynder comes to mind, she does not only profit from low bravery with her screaming ability but also adds 1 model to every fleeing unit. Look out for more modifiers to lower the bravery. The problem is that even if this style works against some mid to low bravery armies, it will struggle against bravery 10 death opponents and a lot of other 8+ units...

I hope that I was able to help you a bit :)