Lulu, the Fae Sorceress

Health: 6, Level: 4
Level 4: {u}{g}: Create a 1/1 legendary creature token with flying and hexproof named Pix.
Levels 5-8: Whenever Pix blocks or becomes blocked, you may replace Pix with another creature you control. If that creature dies this turn, so does Pix.
Levels 9-10: {u}{g}{g}: Put a +1/+1 counter on Pix.
Whenever a creature an opponent controls dies, if that creature blocked or was blocked by Pix in the same turn, level up.