When one of your Walkers attacks, that Walker gets Ferocity until end of turn.
Remove 2 cards from your discard pile from the game Meditate
Keywords
Ferocity
Ferocity: An isolated, static ability that means, "Damage from this unit can't be prevented." Damage that can't prevented includes all damage coming from the unit with Ferocity, including damage from attacks, Ambush, Deflect, Retaliate, and other abilities. Units with Fortitude override this ability, and can prevent damage to themselves from units with Ferocity.
Meditate
Meditate: An isolated effect activated during a POP chance or your build step that means, "You may play this card from your discard pile without paying the printed cost. Play only during a POP chance or during your build step. When this card would be discarded, remove it from the game instead." Meditate can only be activated when the card is in your discard pile. Paying the Meditate activation cost means you don't pay the normal printed cost of the card.