Solesik

This pink-grey worm creature has a segmented body dotted with short horn-like nubs. Its head is dominated by a circular, tooth-ringed mouth, which is surrounded by three flailing tentacles covered in tube feet like the arms of a starfish.

Source: Book of Fiends D&D 3.5 by Green Ronin Publishing

The Solesik is a chaotic evil outsider hailing from the Abyss. This creature is the bane of wizards, sages, and scholars. This fiend feeds upon languages and seeks out any language from written to the spoken form. The Solesik can bite a victim and drain languages from it.

The Books of Fiends actually has very little information on this monster. Only one paragraph which I paraphrased above. This creature caught my attention because it has two interesting mechanics that alter or affects speech. It has a garble field ability which creates language instability and it has the ability to drain languages. I found it unique that languages was used as a resource to be targeted and it kinda made sense. If you can't communicate you are at a severe disadvantage and those who use verbal triggers for spells(clerics/wizards) are effected the most.

Combat: The Solesik is a medium outsider and it is classified as a Challenge Rating 8.

-Garble Field: The Solesik radiates a aura of language instability within a 60ft radius. This aura has a number of effects as listed:

*Any speech or communication requires a partial action instead of a free action. Longer communication requires a standard action. The short communication I interpret as costing a swift action.
*Spells with verbal components require an extra round to cast. Most spell can be cast in one round while in this aura you are spending a second round to get a spell off.
*Intelligence based skills and checks are at -4.

Language Drain: A Solesik drains language from a foe with a successful bite attack. The opponent has to make a Wisdom save vs DC 15 using intelligence as the modifier rather then Wisdom. Failure drains 1d2 languages. If you have multiple languages I assume you roll them randomly to see which ones are drained. For every language drained the Solesik gains a temporary level which last one hours. Adventurers who have had their languages drained can only have them recovered through a restoration spell.

-Spell-like Abilites: At will-command, erase, mage hand, suggestion. 1/day blasphemy, power word stun, word of recall

-Misc. Abilities: Fly, Improved Grab, Demon Traits, Darkvision 60ft, Spell Resistance 18, Telepathy 100ft, Damage Reduction 10/good, etc

In combat you can typically see the Solesik casting power word stun as its first action. Move towards the caster and start working on draining their languages. The Solesik is drawn to those who have the highest number of language slots which typically would be a wizard or intelligence based character.

Encounters:

1. You can use the Solesik as the mastermind behind kidnappings around the city. Scholars, Sages, Wizards, Cleric, etc are beginning to disappears. The Solesik hunger for languages has no bounds. You can drop clues at the seen of various crimes and have the PCs solve the puzzle leading to the Solesik lair.

2. An Academy for upper learning is sacked by the Solesik and a gang of minor demons. The students and the teachers are taken to the basement of the school. The group has to dodge through the university corridors to help liberate the students and end the Solesik reign of terror.