Princess Luna needs to dive into the dreams of Night Light and Twilight Velvet to help bring the spice and sex back into their marriage.

She needs another alicorn to help her but Princess Cadence and Twilight Sparkle are not viable candidates for obvious reasons.

Which leaves Princess Celestia as Luna's wing mare.

Story contains: a lot of Lucid Dreaming and out of body projection, first person point of view memory flash backs and fantasy dreams, ponies talking candidly about sex, Princesses helping enact out sexual fantasies, oral sex, orgasm denial, committing adultery within a dream with the end goal of Good clean hot married sex in the end.