Licids were one of the more interesting twists on creature enchantments. There were twelve licids in all -- five each in Tempest and Stronghold, and two more in Exodus. Below is their (small) entry in the Tempest Block Style Guide.
In the card art, licids were always show attached to a "host." At least one non-licid card contains a licid: Mage il-Vec from Exodus. The John Matson illustration on this card was originally commissioned for a licid. (It's attached to the back of the mage's head.) The Tempest team joked that perhaps it was fashionable to wear licids in Rath.