At the end in the hall, take a leap out onto the ledge to your left . Follow the curvature around the tower until you are directly above another strut that has cracked. Similar to the one above, it may break and you're told to Elden Ring Runes get through it. There's no alternative route to the top of the tower. it did glitch out and it killed me twice before doing no damage a third time. If this happens to you try returning using an alternate route and make the jump until you're safely on the ground next to the elevator. Then, take it to another site of grace, and then, after passing another monk in blackflame, and you'll see the entrance into the Godskin Apostle.
Most of the Apostle's attacks are fairly well-telegraphed, and it shouldn't take a lot of attempts to get into his routine. One of the things that irritated me was an attack in which he rapidly turns his blade his direction like an industrial fan. He then keeps it in place while walking for a massive blow. I was never able to stop him from doing so during this attack, so it's safer to stay at a distance until it's finished. Be wary of when you heal. Godskin Apostle will slyly lob an exploding blackflame at you when you try to sip in your flask.
The second part of the game will feature some Reed Richards stretchy antics, however, they won't disrupt the fight as much as for instance, Margit's phases two moves. Once you defeat the Godskin Apostle, you'll be given the armor of buy elden ring weapons his disgusting appearance, and an item in the next room is filled with the Godslayer's Greatsword.