They appear to be a currency you earn from doing Auchindoun dungeons in Outland. I’ve been getting a fair number lately from running old dungeons. But I can find no information about what you can spend them on. Anybody know?
You get spirit shards when your faction controls all 5 towers in terokkar forest. There’s a vendor who sells items… spirit sage Gartok. He can be found in stonebreaker hold. He sells gems, pots, helms, and rings.