Epiphany Shards are items a Soul-Smith can use during a Relationshift in order to play a guiding hand in the conversation. Each shard is made from a particular Humor, and presumably inspires thoughts and feelings related to traits that humor would normally bestow upon a character's personality. For example, a Flow Shard would help someone calm down, while a Mend Shard might encourage those in the Relationshift to empathize with each other a little more.
These items are meant to help characters straighten out their own inner feelings. However, use of an inappropriate Shard might make the Relationshift take a turn for the worse -- and even using an appropriate one may be problematic if it touches on feelings a character isn't ready or willing to address.