The problem isn't the idea. The idea is fine. The problem is in how it's executed.
Imagine you're a space marine captain or chapter master fighting a slaaneshi warband. Your honor guard get separated from you along with your master of sanctity in the fighting but you can still hear their vox broadcasts and know their location. As you run you can hear sounds from fighting from the vox along with the sounds of screams. You finally arrive but it's too late your squad and the master of sanctity are dead to a space marine covered in scars and in garish pink. He looks at you and you bellow your challenge to him and he happily obliges.
It is no contest between his skill and yours. You are being pushed back with each strike of his quicksilver sword. And just when you are about to lose he trips. Part of you wonders if it truly was an accident but you have no time to ponder it. Lightning quick you thrust your power sword upwards destroying his twin hearts and he falls dead to the ground.
You make way towards your fallen brothers and kneel taking satisfaction that their killer is dead.
After that aboard your flagships things get strange. You wake up in cold sweats and start remembering things you've never experienced. Delightful and horrible things. You consider talking to one of the chaplains but a persistent voice in your head stops you and so despite yourself you don't.
Things get worse. You're making vox calls you don't remember making. In spars with your brothers you injure them too hard. Not hard enough to bring suspicion but hard enough to keep them in the infirmary for a while. Your hair starts to fall out ao you keep your helmet on. You steer clear of the chaplains but you're sure they're starting to get suspicious. It is time the voice speaks into your head and to your horror you find that something else is piloting your body.
You make course towards an asteroid field near where reports of that same slaaneshi warband were seen. You gather your brothers up amongst you with you being the only one in full battle gear. Then ships from the warband appear around your fleet hidden in the asteroid field and you scream in agony as your face joins a myriad of others as Lucius the Eternal is reborn once again amongst your brothers.
The delightful slaughter soon begins.
Many ships were taken from the fleet others destroyed completely and utterly. You don't dare to think about how many of your brothers died. As you scream in silent agony Lucius takes another sip of his goblet of your brothers blood.
