A six-inch metal sphere that floats and is enveloped by an aura of lightning
A Dynamo is a six-inch metal sphere that floats a few feet off the ground and is enveloped by an aura of lightning. This lightning ranges from a pale blue to a deep purple. Anyone who touches the lightning with something conductive (such as a metal sword) must save vs. Spells or receive a -3 penalty on attack rolls due to numbness for 1 turn. This penalty is not cumulative.
A dynamo fires bolts of lightning at its foes. Despite appearances these spheres are quite cowardly, each making a morale check at half health.
Basic Fantasy Field Guide Omnibus