I know that someone on this board has done a compilation of spell mastery options before . I've even quoted it in a post. Yet I can't seem to find it. Can someone point me in the right direction?
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Found it!
https://forum.atlas-games.com/t/collection-index-of-all-spell-mastery-abilities/2026/1
Mastery Ability Page Source
Acute Sense* 71 HoH:TL
Adaptive CastingΨ 99 HoH:TL
Boosted Casting†99 HoH:TL
Ceremonial CastingΨ 99 HoH:TL
Disguised CastingΨ 99 HoH:TL
Fast Casting 87 (83) ARM5:CR
Harnessed Casting†99-100 HoH:TL
Lab MasteryΨ 100 HoH:TL
Learn From MistakesΨ 100 HoH:TL
Magic Resistance 87 (101) ARM5:CR
Multiple Casting 87 ARM5:CR
Penetration 87 ARM5:CR
Quiet Casting 87 ARM5:CR
Stalwart CastingΨ 100 HoH:TL
Still Casting 87 ARM5:CR
Tethered Casting†100 HoH:TL
Imperturbable Casting 33 HOH:S
Obfuscated Casting 34 HOH:S
Precise Casting 34 HOH:S
Quick Casting 34 HOH:S
Unraveling 129 HOH:S
Rebuttal 129 HOH:S
Apotropaic Mastery 122 RoP:TI
- Quesitorial Magic (normally restricted)
Ψ Cult of Mercury (House Mercere)
†Mutante Magic (House Mercere)
Here is one list; I'd welcome any notes on stuff missing...
Mastered Spell Special Abilities in ArM5
The following special abilities are available to any caster:
* Fast Casting, ArM5 87
* Imperturbable Casting, HoHS 33
* Magic Resistance, ArM5 87
* Multiple Casting, ArM5 87
* Obfuscated Casting, HoHS 34
* Penetration, ArM5 87
* Precise Casting, HoHS 33
* Quick Casting, HoHS 34
* Quiet Casting, ArM5 87
* Still Casting, ArM5 87
* Unraveling, HoHS 129, used within the Line of Pralix
* Rebuttal, HoHS 129, used within the Line of Pralix
Cult of Mercury Abilities
The Cult of Mercury teaches certain exclusive spell mastery abilities to its members:
* Adaptive Casting, HoHTL 99, reprinted HoHS 34
* Ceremonial Casting, HoHTL 99, reprinted TMRE 38 and HoHS 34; note that this ability has escaped the Cult's clutches, and is "spreading quickly through House Jerbiton" (HoHS 60).
* Disguised Casting, HoHTL 99, reprinted HoHS 34
* Lab Mastery, HoHTL 100, reprinted HoHS 34
* Learn From Mistakes, HoHTL 100, reprinted HoHS 34
* Stalwart Casting, HoHTL 100, reprinted HoHS 34
Mutantes Abilities
The Mutantes can learn additional spell mastery special abilities that simulate the Virtues of their lineage:
* Boosted Casting, HoHTL 99
* Harnessed Casting, HoHTL 99
* Tethered Casting, HoHTL 100Apotropaic Mastery 122 RoP:TI
Thank you!!! 
Right! Added it and Acute Sense, thanks.
Both of those were listed on the compilation you first posted the link to, Erik.
I thought it better to list the mastery then ask Yair to read the list and figure out what he had missed. (I didn't notice the absence of Acute Sense)
Maybe because it's the first one in the list and thus not absent 
from Yair's list not from "mine"
ah