Toreador Grand Ball/Mask of 1000 Faces

And does the second vampire's action is unblockable?

Thanks, Pascal. Sorry this turned out to be such a headache - certainly not what I was expecting when I first asked the question.

Presumably this also applies to Nakhthorheb and Mask? I ask because your reversal specifies "non-bleed actions," but Nakh's text does not.

Brum wrote:

And does the second vampire's action is unblockable?

Technically, no. But that doesn't matter - the whole point of doing this is to ask all other players to decline blocks while the TGB'd vampire is acting, and then play Mask. The decision not to block is binding (unless bounce is played), and that still applies after you play Mask.

Brum wrote:

And does the second vampire's action is unblockable?

No. But if you're smart enough, you play the Mask after the other players declined declaring block attempts.

Kushiel wrote:

Presumably this also applies to Nakhthorheb and Mask?

Correct. And to Aisling.

The more I think about it, the more I think that action modifiers should not carry on to the Masked vampire. That would eliminate the need for the current two-dozen-or-so current rulings.

The text of Mo1KF assumes that action modifiers modify an action, when in fact most modify the acting vampire during the action. The term "action modifier" is imprecise: stealth and bleed are characteristics of a vampire, not an action. Lost in Crowds gives the acting vampire +1/+2 stealth; it doesn't give Govern the Unaligned +1/+2 stealth. Felicia Mostrom doesn't block Govern the Unaligned; she blocks Gilbert Duane (hopefully )

Based on this logic, there is no reason for action modifiers or effects to "carry over" from one minion to the next except a misinterpretation of the term "action modifier". Reactions aren't considered to modify the action, so I don't see why action modifiers would, either, other than the name. Action modifiers are simply cards playable by an acting vampire during an action, just as reaction cards are card playable by a reacting vampire during an action.

By removing this sentence: "Not usable if any action modifiers or other effects have been used that could not have been used if this vampire were the acting vampire.", and understanding that action modifiers stay with the minion who played them, Mo1KF becomes much, much easier to manage.

The phrase 'Not usable if any action modifiers or other effects have been used that could not have been used if this vampire were the acting vampire' implies that you would need to test whether the 2 vampires could have been exchanged in the action without consequence.
If an effect (such as inherent stealth or TGB) causes a difference in options for the blocker, then Masking can not be played.
I believe that this is in accordance with the intended mechanics of the card.