How to upgrade Zaj armor to X-Grade

I am looking for info on upgrading Zaj S80 to X-grade armor. I am guessing it is the vender at sky castle that it says is there only when player owned. If this is the case could someone tell me where at sky it is located and if it is in castle will I have to fight really strong monsters to get to it?

It is located on a small island to the north of the sky castle, you can get to it without any agro monsters.

You can get to sky castle by using a scroll purchased from the shop in SKT

This npc has been moved to inside of the sky castle when player owned.

The way to tell if sky castle is player owned is by either asking on global or using a scroll of sky castle and seeing a teleport npc at the warp in location.

this npc can teleport you into the sky castle where the crafting npc is and also where the new gem npc is located.

Furthermore you can walk into the statue in the middle of the room and it will teleport you to sky gardens. A new hunting ground inside a safe zone.