The Living Crossbow

A weapon from a far off land., it appears to have
been made from some sort of unknown creature.
Functions as a light crossbow, once per day can
be used to inflict 1d6 of a random damage type
onto a successfully fired shot. This damage is
also applied to the user. Requires a Int DC 10
check to understand how to activate.
1d8 Piercing, Range 80/320.
But why does it skitter when you hold it?