I did a 10 level version for a tabletop game.
I repeated the bonuses at odd levels. At the 6th it gained a projection so it could harass players a little more directly. It got it's own Ooze pet and for a capstone it gained Guard & Wards as well as Black Labyrinth, both 1/day with a duration in minutes, Lord/minions immune (the lab was boss room only).
Steal w/e ideas you like.