now that youve clicked on this topic to up to the top left of the sreen where it says "ironworks gaming" it shows a picture of Irenicus killing the 3 cowleds. what spell is he casting? if i remember correctly the info. bar sais he is casting flesh to stone but what the heck? doesnt look like any spell ive EVER seen?

Errr...what? Nah, the spell effects for Irenicus are flashy to show he's different.

Power Word Kill

They're unique spells. They're called things like "Power Word: Kill" and "Finger of Death" but they're not the ones you memorize and scribe. They're variants with flashier effects and, unless the target is immune to almost everything ( Arkanis Gauth in his nastiest form comes to mind) they kill with no save, regardless of HP.

I have heard that Irenicus occasionally casts some kind of über-necromancy spell known as "Rapture of the Father".

BIG ASYLUM SPOILER!
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Rapture of the Father is the spell he casts in the Asylum to steal souls.

True. Spells casted during cutscenes are not those you can memorize (imagine Irenicus casting all those killer spells at thieves who succeed their saving throws).
For example, browse spells with Shadowkeeper: there are six Flesh to stone spells, seven dominations, ten dispels, twelve lightning bolts... These are used by different creatures (golem's haste is not the same as wizards or Mazzy's) or in some scripts (Irenicus spells are more powerful than standard ones).

Arkanis Gauth? i just saw him when i tried to kill aran linvail...who the heck is he?

That's what I've been asking :(
WHO IN THE NINE HELLS IS ARKANIS GATH?!?!

He is an über-NPC assasin that prevents tou from killing Shadow Thieves after you have sided with them (prevents you from eliminating all posibilities to reach the Asylum.