In addition to Elden Ring Runes the poisonous items you've included in your inventory climb up to the boss of Night's Cavalry and throw it a volley of two or three items, then sprint across the hill towards the north. This is a trail that is full of poison traps, as well as smaller enemies that jump out at you. In themselves, the enemies can be simple to avoid, however, it is best to activate the traps while keeping an army of Night's Cavalry hot on your trail. Your aim is to be able to get the Night's cavalry boss poisoned, because then the health of the unit will continue to tick down. Be careful to avoid its attacks while riding up the hill. If your armor has decent immunity, you can most likely stay safe from poisoning yourself, but pop a Neutralizing Boluses if you do get poisoned.
When you've reached at the summit of the hill at the top, the Night's Cavalry boss will either change its mind or appear at the bridge, but will remain in its poisoned status. Return to the bottom, hit it with another poison pot, and repeat the cat-and-mouse race through the hills. At some point, the poison wears it down and it'll go to sleep, rewarding you with 40000 runes and Bloodhound Step.
It's possible you won't need to wait for long until the poison has finished doing its work The poison had taken off half of the evening's Cavalry boss's health when it just randomly passed away on me. I've read about the same thing happening for other gamers. When you respawn, the poison status applied may make the boss immediately die. However, even if it does not but happen, the poison is sure to perform its job.
This isn't the only way to defeat the boss without having to drag out a fight.
You can also climb onto the tree that extends over the bridge , and then attack the boss using ranged weapons or magic spells to whittle off his strength.
You can probably make him fall off the bridge and to his final destination with the right moves (this is certainly possible with the Night's Cavalry from Limgrave).
But the poison method is definitely effective if you are not afraid of Elden Ring Runes fighting hard and dirty. This is an FromSoftware game where anything is possible.
