New Mob idea for next update

My idea for a new mob in the next update (fake update from me, Sky adventure update, for example) should be call the Wraith, a flying mob that can spawn in daylight to nighttime and can spit ghast fire balls at you. HOWEVER, they can only spawn when a certain achievement is unlocked called the "Oh Derr" where you have to kill ten phantoms and use their drop to fix your elytra, so this might be late game people.
Thanks for (possibly not) looking at my idea and please give me credit, you can design it however you want Minecraft.

--Bowserland123