Garruk, Savage Herald — ruling 1

If either creature is an illegal target as Garruk's second ability tries to resolve, the creature you control won't deal damage to any creature.

Garruk, Savage Herald — ruling 2

When assigning combat damage, you choose for each creature whether you want to assign its damage to the creature blocking it, or if you want to assign it to the player or planeswalker the creature is attacking. You can't split the damage assignment between them.

Garruk, Savage Herald — ruling 3

Garruk's last ability affects only creatures you control at the time it resolves. Creatures you begin to control later in the turn won't gain the ability.

Garruk, Savage Herald : règles, fonctionnement et interactions (MTG)

Garruk, Savage Herald is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

+1: Reveal the top card of your library. If it's a creature card, put it into your hand. Otherwise, put it on the bottom of your library. −2: Target creature you control deals damage equal to its power to another target creature. −7: Until end of turn, creatures you control gain "You may have this creature assign its combat damage as though it weren't blocked."

How it works : Garruk, Savage Herald

Original English text — Wizards of the Coast / Scryfall

#1June 23, 2020· Wizards of the Coast
If either creature is an illegal target as Garruk's second ability tries to resolve, the creature you control won't deal damage to any creature.
No other card is named in this ruling.
#2June 23, 2020· Wizards of the Coast
When assigning combat damage, you choose for each creature whether you want to assign its damage to the creature blocking it, or if you want to assign it to the player or planeswalker the creature is attacking. You can't split the damage assignment between them.
No other card is named in this ruling.
#3June 23, 2020· Wizards of the Coast
Garruk's last ability affects only creatures you control at the time it resolves. Creatures you begin to control later in the turn won't gain the ability.
No other card is named in this ruling.

Interactions with other cards

These cards' text mentions Garruk, Savage Herald.

Garruk's Warsteed

Vigilance When this creature enters, you may search your library and/or graveyard for a card named Garruk, Savage Herald, reveal it, and put it into your hand. If you search your library this way, shuffle.