Random idea: What if the targeted creature gained spell damage? The idea behind that being that the buried creature "dies", but still attacks as a vengeful spirit from beyond the grave.
So, "Premature Burial" would do the following.
1. Burrow target creature, halving it's attack and making it untargettable
2. Target creature now deals spell damage
3. Trigger death effects
Seems overly complicated, but maybe the idea could be refined/simplified. At the very least, I think it would distinguish the card from the other "forced burrowing" ideas that everyone talks of.