Voice of Dark Gods [Pathfinder]

[Kulture]

I've been digging for a while and haven't really found much yet to find a satisfactory ruling on something.

What would you say would be a fitting effect for being told Nyarlathotep's true name or seeing his true form in a setting without sanity rules?

In mythos canon being told his name drove one particularly mentally resilient man into very severe insanity, taking years to recover and the same man died outright from even catching a glimpse of Azathoth's court.

My reasoning is that there is a character within a game I'm in that is currently a host to an aspect of Nyarlathotep (The Forgotten Shadow, sort of a cross between the Black Pharaoh and the haunter in the dark and The Darkness) and he's an alchemist/assassin
One of his many infusions is vocal alteration and his assassin spell is Mimic voice.
Whether either of these spells would go as far as to allow him to pronounce the name in question is a point of contention in itself but neither spell states a limitation on how far a voice could be altered.

Is there a consensus or previous example of such an effect in D&D?
Even if it becomes a moot point I'm curious of the input.

[Bhaakon]

If you want to be cruel in the spirit of the source material, pick one of the diseases from the madness chart (http://www.d20pfsrd.com/gamemastering/afflictions/madness) (paranoia or schizophrenia seem appropriate) and have the PCs roll a will save against it. Players who fail develop that disease, those who succeed get off with 1d6 Wis damage (which, of course, makes it harder to resist next time).

If you want something more in line with the game (ie: less likely to get dice thrown at you), symbol of insanity works, but lacks the permanence.

Or you can just import the 3.5 Sanity system.

[Kulture]

I've run across something somewhat similar, though smaller in scope.

Dark speech allowed a user to instill fear, control vermin swarms and weaken items at the cost of stat damage.

As for the idea of leniency, it's a strange circumstance.

The person trying to use this ability is a PC, the player of whom asked me to look into a viable suggestion for the effect for the DM to mull over.

It's a very high power campaign, they're currently fighting what is thought to be a Thanademon disguised as a king who is currently immune to normal forms of damage due to a ritual enchantment that allows him to feed off of negative emotion.

The player thought this may be a good idea to cripple the creature, since its followers were no-selling 84 damage crossbow crits.

I got tasked with this because I have most of 3.5's books in PDF and I'm big on Nyarlathotep's lore.

I've already advised that they ask the DM's permission to devote themselves to Nyarlathotep as an elder evil in order to pick up dark speech and evil brand.