Tasty Morsel
Once per game, when Karina fails a Bloodlust roll, she may choose to bite an opposition player with a ST of 3 or lower as if they were a Thrall Lineman team-mate. Karina may note bite Star Players with this special rule.
Tasty Morsel is one of the special rules that you have a bit less control over, though if it comes into play will be a helpful but unplanned ability. It requires Karina to be in base contact with an opponent of ST3 or lower and then you also have to fail the Bloodlust roll. If these two things do occur in your game, then I would use the ability at the first opportunity. It wouldn’t surprise me if there are games where you don’t get a chance to use this at all, so it makes sense to use it right away.
This will let you take down an opponent and then still use Karina for something extra that turn. At the time of writing we don’t know the wording on the Bloodlust ability, which might open up further rules questions.
Bloodlust now requires you to bite at the end of your turn (or immediately before scoring/passing/handing off), so no need for Karina to be in base contact first. This means you could potentially use her to blitz off a cage corner, step into the cage and then bite the carrier, all in one activation. Obviously not reliable but potentially devastating.
I’d not really given this much consideration. You could instead Hypnotise a cage corner and go straight in and bite the ball carrier.