Well for the crowns you get Master's circle which is an accessory which gives 100%
resistance to all elements and +30def, i think it does something else but ill leave that
for someone else to answer,
As for all 250 nobody sigils im unsure, I have reason to believe its a Gear though, (Ive
only got 234 so far)

Hope this helps

-Thyphix-

i got the masters circle already i want to know what do you get from the challenges

you get an ultima panel that links to your weapon. and it's 255 sigil.

You get an Ultima Weapon panel for 255 sigils. It increases attack by 15.

Masters Circle is not the best ring to me cause when you have red health you cant heal at
all and when you miss with an attack you lose hp. I used to just use it for Xion's
Ragnorak and her awesome attack on Final Form but I figured out that nil is the thing that
blocks those attacks...