An opponent cannot block and kill Klauth or Soul of Windgrace.
Soul of Windgrace does not have summoning sickness.
You have at least one land card in your graveyard.
Steps
Declare Klauth and Soul of Windgrace as attackers, triggering their abilities.
Resolve the Klauth trigger, adding at least ({7} magic symbol) ({RW} magic symbol) ({RW} magic symbol) that can only be spent to cast spells.
Resolve the Soul of Windgrace trigger, returning a land card from your graveyard to the battlefield tapped.
Move to your postcombat main phase.
Cast Waves of Aggression from your graveyard for its retrace cost by paying ({3} magic symbol) ({RW} magic symbol) ({RW} magic symbol) and discarding a land card, causing you to untap all creatures that attacked this turn, and to get an additional combat and main phase after this one.
Repeat.
Results
Infinite colored mana that can only be spent to cast spells.