An adaptation of the Vile Scholar theme from the Book of Vile Darkness, with inspiration for powers and abilities taken from a variety of other existing themes.
Called of Cthulhu
"Ph'nglui Mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn!"
There are things mortals were not meant to know. And you dream about them every night! Because a funny-looking green guy with an octopus for a head keeps showing up in your dreams and telling you them, in a language that sounds like the slapping of cold, briny tentacles.
Maybe he tells you to go to a sunken city, filled with the chants of fish-people and cultists. Maybe he says humanoids are delicious, and you really should find out yourself. Who knows! The people you tell about your dreams tend to go mad, and not in the fun way, either.
The language and mindset of squamous, otherworldly horrors no longer seem otherworldly or horrifying to you. And when you describe your dreams to other people, it does unpleasant things to their minds and bodies.
Benefit: You are fluent in Deep Speech. In addition, you gain a +2 bonus to Dungeoneering checks, and to Bluff checks, Diplomacy checks, and Intimidate checks made while interacting with Aberrant creatures. You also gain the call of Cthulhu power.
Call of Cthulhu -- Called of Cthulhu Attack
The nightmares brought to mind by your utterings drive your opponent into a screaming, panicked frenzy.
Encounter * Fear, Implement, Shadow
Target: One creature that can hear you
Attack: Intelligence, Wisdom, or Charisma vs. Fortitude, Reflex, and Will. You make a single attack roll and use it against each defense.
Hit (Fortitude): The target falls prone.
Hit (Reflex): You push the target up to its speed.
Hit (Will): The target grants combat advantage until the end of your next turn.
Level 5 Feature
Your memories of the sunken city make underground ruins seem safe and cozy to you. Slimy Underdark dwellers show up in your dreams often, and you know their names as well as their powers.
Benefit: When you make a Dungeoneering check, you can roll twice and use either result.
Level 10 Feature
Most people would have nervous breakdowns if they were to suddenly sprout tentacles. Fortunately, yours are helpful and friendly, and they go away when you don't need them.
Benefit: Once per round, you can retrieve or store an item as a free action instead of a minor action. You can also use one of your tentacles to hold an item (like a lantern), to open doors, or to do things that don't require fine manipulation, but you cannot make attacks or roll skill checks using it.
Level 2 Utility Power
If you want to visit that sunken city from your dreams, it might help to bring your friends along ... and to be able to breathe underwater. Fortunately, you've got that covered. Just make sure to tell them first, or they might be caught by surprise!
Deep One Transformation -- Called of Cthulhu Utility 2
Your skin becomes slimy and scaly, and cold, pulsating gill slits appear on your neck. Everyone nearby is affected as well, and the unprepared are REALLY affected.
Daily * Shadow, Implement, Stance
Close burst 1
Target: Every creature in the burst
Attack: Highest mental ability score vs. Fortitude
Hit: 1d6 + Highest mental ability modifier damage, and the target takes ongoing 5 damage as long as it's not underwater (save ends).
Special: Allies in the burst do not take damage from this power. Instead, they assume the deep one stance. Until the stance ends, they can breathe underwater and have cold resist 5, but are unable to breathe air. You may choose to assume this stance as well.
Level 6 Utility Power
You understand the geometry of madness well enough to plunge into the depths of your dreams, and interact with the nightmares therein. Sometimes they tell you something useful, but other times their answers leave you shaken, and you wake up in a cold sweat.
Dreams of Madness - Called of Cthulhu Utility 6
You ask questions of one of your nightmares, and hope that you can withstand the answers.
Daily * Shadow
Requirement: You must use this power during an extended rest.
Effect: You may ask up to three questions of Cthulhu or another Far Realm aberration. For each question, make a check with a bonus of 5 + one-half your level + your highest ability modifier, against a DC your DM secretly sets.
On a successful check, the nightmare gives a useful (or at least harmless) answer, which you remember when you wake up. If the check fails, you instead lose a healing surge, which is deducted from your total when you wake up the next day.
Level 10 Utility Power
The tentacles you sprout are friendly to you and your allies, but they don't care for your enemies much at all.
Squamous Tentacle -- Called of Cthulhu Utility 10
You know how to fight with your cephalopod appendages just as well as with your bony limbs.
Encounter * Shadow
Effect: Until the end of your next turn, your reach increases by 1, and you gain a +2 power bonus to melee damage rolls.