When you Warcry a unit or weapon, reduce its cost by that much.
Valkyrie Ally: Warcry 2.
Card sounds may differ from in-game as they get updated.
Warcry - Each time a unit or Relic Weapon with Warcry attacks, it grants a permanent bonus to the top-most unit or weapon in your deck. Even if it's a few cards down, you'll get to stack up the bonuses on it over multiple turns.
Ally - Happens as soon as you have a unit of the named type. This can be when you play the unit with Ally or later if there's none of the needed type in play. Ally resets if the unit dies or is returned to hand.