Convocation's Child

While you have a wiggly cube as your familiar,
it gains additional maximum HP equal to your
warlock level.
When you reach level 6, you can choose to have
your cube grow to a Medium creature, and
Large at level 14, as a bonus action.
Whenever it is Medium, it's Engulf damage
improves to 2d8 initial damage and to 4d8
at the start of the cube's turn, and 3d8, and
5d8 at Large, respectively.