Ophiocordyceps

Destroy target creature. If a creature destroyed
this way had power 2 or less, you gain 4 life and
draw a card.
The Ophiocordyceps unilateralis fungus has just one
goal: self-propagation and dispersal. Researchers think
the fungus, found in tropical forests, infects a foraging
ant through spores that attach and penetrate the
exoskeleton and slowly takes over its behavior.