Centaurian slug

The Centaurian slug is a small parasitic creature used as a means of torture and interrogation. It enters the host's body through the mouth, then attaches itself to the brain stem. Once attached, it secretes a toxin that functions as a truth serum, preventing the host from being able to withhold any information when asked. The centaurian slug's anatomy and lifestyle bears similarity to the Ceti eel.

History
In 2258 of an alternate timeline, the Romulan criminal Nero had Admiral Pike in captivity. Nero inserted the slug into Pike in an attempt to glean the frequency of Earth's border protection grids from the admiral. Due to the influence of the slug, the interrogation proved successful.