In the ongoing search to find musical treasures, Sandcastle provides a reliable source of riches. The band’s latest EP Bloodstone Mermaid exudes a mystical, enchanting, glam-folk level of intimacy. A pensive, candlelight aesthetic envelops the softly-sung, spindly-strummed selection, retaining a delicate, engaging fragility. On Thursday, April 12, Sandcastle will be performing at Ortlieb’s as part of a lineup that alo includes Line Leader, Cookie Tongue, and Cóq.