Bloodseeker Hydra

Bloodseeker Hydra cannot have vigilance.
As long as an opponent has less than their starting life, Bloodseeker Hydra gets +1/+1. If an opponent has 10 or less life, Bloodseeker Hydra instead gets +3/+3 and has trample.
If Bloodseeker Hydra kills a creature during combat on your turn, it doesn't untap during your next untap phase.