Hexproof from black
Whenever Garruk's Harbinger deals combat damage to a player or planeswalker, look at that many cards from the top of your library. You may reveal a creature card or Garruk planeswalker card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.
Hexproof from black means that Garruk's Harbinger can't be the target of black spells your opponents control or abilities your opponents control of black sources.
If Garruk's Harbinger deals damage to a planeswalker greater than their loyalty or to a player greater than their life total, you look at a number of cards equal to that full amount of damage dealt, not just that loyalty or life total.