The boss fight of fighting 3 Ruin sentinels is quite difficult. The fight tests your defense and agility, so you have to be calm and use a decent shield. The sentinels are vulnerable to magic, bleeding, lightning effects. Make sure to coat your weapons to have an edge on the fight. Wearing a cat ring might come in handy because when you jump you dont take damage.
First, when you jump down on the small floor, you will fight only one sentinel, after you kill him, the second sentinel will jump up on the floor and will fight you. You will have a brief window of time to fight the second sentinel alone until the third will join him. Make use of this window to attack him hard. Then jump to the ground floor and make use of the wide space to dodge attacks.
Make sure when you fight the first sentinel dont fall down because it becomes very hard to fight all three sentinels at once.
