Neurotyrant

As long as it is your turn, tyranids you control get +1/+0, or +2/+0 if half or more of an opponent's creatures are tapped
Whenever Neurotyrant or another tyranid with a higher toughness than power you control blocks, put a stun counter on the blocked creature
At the beginning of your upkeep, choose 2 other Tyranids you control, they gain hexproof until the beginning of your next turn