The lake is a body of water which is coalesced cognizance of Devotion, one of the Shards from Sel. So to nswer your first question, yes, it is a manifestation of a Shard. To answer the second, probably not, though your question could be stretched to mean whether or not Devotion could reunite other Shards, which could be a maybe since Odium found a way to Splinter them.