The King in Yellow places down a Yellow Sign, cursing the first person to gaze upon it to become his next target. When this ability is first leveled, a ward will appear randomly on the map. This ward will be a Yellow Sign. The first enemy god to walk into the Sign's range will be marked with the Yellow Sign, and the Sign will disappear, and reappear in a new random location. The King in Yellow can also chose where he wants to place a Yellow Sign. while his ability is toggled, any ward placed will gain the properties of a Yellow Sign, and the randomly placed Sign will disappear. This placed Sign will function the exact same as one that was randomly placed, and once triggered, it will disappear and a new random Yellow Sign will appear.
Gods marked with the Yellow Sign will suffer additional affects from The King in Yellow's abilities, and will always be revealed to him. In addition, only one god can be marked at a time. If a new god is marked, the previously marked god will return to normal.
When The King in Yellow gets a kill or assist on a god marked with the Yellow Sign, he will create a Brother of the Yellow Sign.
A couple suggestions:
It seems like his kit does not introduce a lot of possibility for counterplay, which in my opinion is what makes the game fun. I suggest changing his Mantle and Mask to affect a targetable area rather than all nearby Gods. In general it seems like most of his abilities just kind of toggle on and don't have to be aimed, meaning the player has to know when to use them, but there is no skill in how they use them. Along this line, his two doesn't seem to have any active effect? You may want to add something just so he would be more fun to play.
My other suggestion is to somehow make it so that he can choose which lane the Brothers of the Yellow sign span on. Allowing the player to choose will allow from a lot more depth (split pushing strategies, early game wave clear, etc.) And I think that added depth an engagement will make him more fun.
Overall, love the concept! If you get a chance to comment on Sisyphus or Robin Hood, I'd appreciate it.