You need to learn to edit your posts instead of double and even tripple posting. It's quite annoying and spammy.

As for the topic, you found your issue. You can just buy +1 PR and not risk automatic perils. You can also just get a Warp Staff to use Unfettered without risk of phenomena instead of using BI on Fettered with risk of perils and get a net profit of PR. There's really no good reason to use BI besides "flavour reasons".

And the +20 from BI is on top of the +10/X of Bound/Unbound. If it replaces, it would say.

I recall reading somewhere within the books that certain rituals require Blasphemous Incantation, though I can't confirm that. Still, that would be an additional reason to take it.

I recall reading somewhere within the books that certain rituals require Blasphemous Incantation, though I can't confirm that. Still, that would be an additional reason to take it.

Nope. Incorrect.

The more I look at it, the more I'm convinced that it's really only useful for a tzeentch-aligned Sorcerer, and only in the unfettered pseudo-push that Bogi crunched the numbers for already.

If you're tzeentch aligned it's cheaper than a new level of PR, so there's that. I guess it can also be used for high-tier, already-at-PR-10 mega-pushing. Seems silly though.

I still have the nagging feeling that we are overlooking something here. But what I have no idea. Maybe it was meant to be a Tier 2 Talent?

(I have the same feeling when I look at Bulging Biceps and Autostabilized, which seem to do almost the same thing, but the different wording must mean something. But I can't figure out what.)

Different things. Autostabilized is a trait. Bulging biceps is a talent. Same end result though.

The mutation that grants autostabilized is pretty useless to a Space Marine tho...

You never want a 10% chance of inducing automatic Perils for an extra +1 PR. Simple as that. No Tzeentch-aligned psyker worth their salt would waste XP on the talent in my opinion. I'd not get it if it was a tier 2 talent, and likely not even if it was a tier 1 talent (maybe due to alignment reasons, not for actual usage unless I felt particularly suicidal).

I still have the nagging feeling that we are overlooking something here. But what I have no idea. Maybe it was meant to be a Tier 2 Talent?

(I have the same feeling when I look at Bulging Biceps and Autostabilized, which seem to do almost the same thing, but the different wording must mean something. But I can't figure out what.)

Bulging Biceps and Autostabilized are essentially legacy problems - in Dark Heresy, Autostabilized granted to option to use Full Auto as a Half Action (and fire heavy weapons unbraced). When the combat system was modified for Black Crusade, Autostabilized essentially became synonymous with Bulging Biceps, but didn't get replaced by it.

As for Incantation... no, I think it's just plain crap.

It's a weird talent.

Maybe they just didn't think it through. It should be errated somehow and made to do something, esp. because Words of Power are a big sorcerous thing,