From LSWiki

With higher necromancy skill, multiple devilflies can be conjured. The level of the summoned devilfly is around 5 with minimum skills.

Your familiar must be alive and present in your environment for this charm to work. The remains of a rat are required to activate this charm.

The devilfly itself is intangible, does entropic damage, and can fly.

Usage

concentrate on conjuring a devilfly