FINALLY! I beat King Master Coco's Trial. GOD DAMN is the Wyvern fight a god damn ring check. It WILL waste rings in the fight, and even more if you're not careful. But, I finally got the golden run where phase one was dealt with quickly and phase two had me combo-parry out of situations so I could keep beating ass. I learned the bastard has a third counter attack if you don't go for the throw and parry him again when he does a tail whip. It was so sudden, I couldn't protect against it properly. But, he went down quick enough, making the Knight fight practically a cakewalk.
Now that it's done, I'm free to play as all four characters at my leisure, clean up any mini-puzzles left behind, and proceed to the secondary ending at my discretion.