Shards, described as "a poor man's cores", are smaller pieces of the same material as Cores. They cannot retain the great power of the Cores, but smaller amounts of energy.
They are originally scattered throughout the Wilds by Caelondian explorers, with the hopes that those areas may someday be colonized. After the Calamity, the Shards possess just enough energy to stabilize their seeded locations, much like Cores. Therefore, once a Shard is removed, the area falls apart.
The Shards upgrade buildings, unlocking more and/or better features.