Crystals are a hidden collectible item in My Little Blacksmith Shop, which currently serve the purpose to [redacted]
Overview
Crystals are mysterious items found throughout the game world.
The crystals have a use, but are not a main story point yet, But according to the Devoloper, Dasius, they will eventually be a main focal point for the game's story. [1]
The Four Crystals
There are Five known crystals as of the 0.0.9e update. They are the Dark Crystal (Fear), Light Crystal (Protection), the red/orange crystal [fire], and the blue crystal [water], And the Green Crystal [Earth].
In order of appearance the crystals are the Light Crystal, Fire Crystal, Dark Crystal, and Water Crystal.
The Crystal's use.
Contained inaccuracies and spoilers, Section was changed.
They have a use, and it isn't just "being lights" Searching for the answer is part of the fun.
Side-Note - If your crystals are flubbernucked, Slipcor's v0.0.9e save-fixer has a feature to reset them.