1) In Tolkien's works, the Sindar are the "grey elves". They were originally part of the Teleri, one of the three clans who went west, but they followed Elwe, who found the Maia Melian in the woods of Doriath and who remained in Middle-Earth. The Sindar were the only elves in Middle-Earth until the Noldor returned, and were relatives of the Teleri killed in the Kinslaying; their relations with the Noldor were therefore strained.
2) In Suikoden, a long-lost race who (according to Richmond the private eye) came down from the north, crossed the whole of the world - leaving ruins wherever they went - and then mysteriously disappeared. The ruins are monster-infested but also contain powerful and dangerous magic treasures. The Sindar also left behind ancient texts which appear in Suikoden II as valuable antiques. Several characters, such as Lorelai and Killey, are seeking the Sindar.
In both cases, the Sindar are an elusive and mysterious people.