Anivia came first.

Anivia was the first champion I worked on at Riot, back when I was an intern. I had only been at the company a week by that time, but due to the rapid rate of champions we needed to put out I was asked to get her into a design-locked state in just two weeks. While Guinsoo had done an initial pass on her design, there was a lot of work that was needed, and the direction I wanted to take her demanded a bunch of new tech as well. She was the first time we attempted to have multi-stage spells (her Q), and the idea of a toggleable ult that drained mana was an entirely new idea in the game at the time. Polymorphing into an egg was basically untested tech, and initial implementations of it were incredibly brittle. In particular at the time “Cleanse” would remove all negative debuffs from a character, and was the bane of my existence.

In one playtest I remember casting cleanse would permanently remove the tracking buff I used to check whether you could egg again or not, rendering the player immortal. Fixing that bug causes another issue where the player would only egg once, but when they turned back into Anivia they had no spells at all. Fixing that bug caused an issue where the player would stay an egg forever but still be able to move and cast spells as normal, and my attempt at fixing that bug made the passive work, but as soon as you died you would respawn as an egg who could move and cast spells. Plus you were immortal.

You don’t know fear until you are being chased around Summoner’s rift by an immortal egg with infinite mana, an on-demand stun, and a wall spell that can and would teleport you to unknown locations on the map if you got hit in just the right way.