Crystal Wisps are small, floating creatures that resemble a Vis crystal encased in some sort of glowing bubble. Depending on the type of wisp, they can have varying attacks, such as poison (Earth wisp), lightning (Air wisp) and others. Wisps spawn in areas with a high concentration of whichever Vis type they are comprised of, and their drops will correspond as well. Wisps will drop 1 or more Vis crystals of their current type when killed, and will follow you if attacked. Tainted wisps, however, will ONLY spawn in chunks that have a particularly high taint aura (50%+ or so), and will drop Tainted vis crystals
They may also drop a cracked wisp shell, an artifact classificated as forbidden.
Fighting a Wisp:
To Fight a wisp it is my recommendation that you first hit with a sword, run away quickly, then hit it with a bow or crossbow.