By outfitting Avenging Druid with Lavamancer's Skill, you transform the creature into a sharp-eyed Wizard capable of pinging an opponent directly on demand. That initial point of damage triggers the Druid's innate ability to dredge through your library until it hits a land, dumping any nonlands straight into your graveyard. The moment that new land enters the battlefield, Retreat to Coralhelm springs to action with its Landfall ability, neatly untapping your Druid so the cycle can begin anew. By looping this sequence, you will rapidly empty your library, flood the battlefield with every land your deck has to offer, and set up a wave of near-infinite damage and self-mill.