By exiling a card type with Semblance Anvil when it enters the battlefield, you permanently discount the mana value of matching spells, which allows you to cast Ghostly Flicker for just a single blue mana. When you cast it, you target Greenwarden of Murasa and a mana-producing permanent, blinking them both out and back into play. This triggers Greenwarden of Murasa's enter-the-battlefield ability to pluck Ghostly Flicker right back out of your graveyard into your hand, while the mana source refreshes your pool to cast it all over again.