I worked out a few of the mechanics if it helps:
- Eating more that one enemy at once will fill the special ability bar (and regain more health than you lose from the teleport)
- if you get hit, it will take a while before the special ability bar starts filling again
- There's a small health regen, so if you might have to go into "evasion" mode (WASD and shift, no teleporting) while it refills