From a strict standpoint, "prevents spell interruption provided you are hit and block with the shield while casting the spell" could imply that if you began casting a spell and blocked the first attack against you with the shield, from that point onward your spell was uninterruptible. I've ran into several players who were unsure of this, so I decided to post a quick counterexample.
The portion of this article that claims Shield Mastery gives a simple 4 TP per shield block is just plain wrong. I tested this again with a PLD25 today, and he gained exactly 3 TP per block. -Ubiquitous42 00:30, 28 March 2007 (EDT)
I was testing this last night and one shielded attack generated 6 Tp for me. I was a 75Pld/37Whm and was using a Master Shield and not using AF feet.
A small comment on spell interruption. There is a small portion in the early casting percentage which is 100% uninterruptable from direct melee contact. Anyone who had to level nin to 37 knows what i'm talking about. If the first attack of a double or triple attack lands in this time, following attacks of the same double/triple. (H2H also included) will also be considered to have landed in that uninterruptable region. However, if a shield block occurs on the initial hit, (such as a mandragora's 1st punch) then if the 2nd attack lands past the uninterruptable phase, you may still be interrupted. I do not remember this occurance prior to the shield mastery patch, but its possible i was less attentive. Other than this occurance, all blocked attacks that i have seen cause spells to be completely uninterruptable. -Silvara
It doesn't seem like it's completely 100% when you block with a shield. I've been interrupted multiple times while casting and blocking with a shield and I still get interrupted once in a while, though this is only with Shield Mastery I. --Radiënt 12:34, 25 November 2007 (UTC)
In regard to the effect of phalanx on shield mastery[]
I have noticed this while skilling up on mandragora in abyssea and other areas. i will be rapidly gaining tp from blocking (i can WS every 3-5 seconds with 15+ mandies and reprisal, PLD/SCH. and yes, the time is correct. using requiestcat, i can start a new WS as soon as the first animation ends, often with 120%~ tp). i take 0 damage from all but a tiny percent of critical hits (5-10%), but i gain tp from almost every attack landing on me, if blocked. more testing is needed, but i am guessing that the effect of phalanx on this ability was changed. i noted that using stoneskin completely stops all tp gain from shield mastery, and will not wear off until its natural duration expires (i still take no damage due to phalanx). Rhionhi 23:14, January 13, 2013 (UTC)
JP Info on Shield Mastery[]
Someone more literate in Japanese wants to take stab at seeing what info (if any) should be added from this source? --Itazura 19:42, 11 August 2007 (CDT)
Store TP and Shield Mastery[]
Store TP Does not effect Shield Mastery in anyway, Tested with Samurai Roll with SAM in party, Which is a SIGNIFICANT increase in Store TP, and i didn't see a Difference, However It could go unnoticed due to the small amount of TP gained by Shield Mastery... -Karbuncle