Daring the Dawn and then Mask of a Thousand Faces
The effect of Daring the Dawn carries over the new acting minion. This means that the new acting minion cannot be blocked by vampires, and will take the aggravated damage after the resolution of the action.
The former acting minion is not involved anymore, as if it never had been the acting minion (despite any blood spend before playing the Mask).
All effects that had been applied to the action or the acting minion carry over as if they had been applied with the Masker as the acting minion.
If Daring the Dawn would be written as below it would make more sense for it to also be carried over to the masking minion:
[for] Vampires cannot block this action.
Mask of a Thousand Faces text "The action continues with this vampire as the acting minion." changes who is the acting minion for the action not the targets of previously played cards/effects.
One could also argue that if Daring of the Dawn has been played the action can´t be masked anymore for the same reason as Aching Beauty... (similar text wise using "this") per ruling if Aching Beauty effect has been activated on minion (A) the action can´t be masked even if the masking minion (B) also has an Aching Beauty.
Name: Aching Beauty
[Jyhad:U, VTES:U, CE:U, KoT:U, FB:PTo3]
Cost: 2 pool
Put this card on any Toreador. If this Toreador is blocked, the blocking minion's controller burns 1 pool before block resolution.
Artist: Dave Roach & Pete Burges; Chris Stevens; Dave Roach & Pete Burges
Any minion can mask before the Aching Beauty on the first Toreador
is activated (i.e., before the pool is burned).
After it is activated, only a minion with *that* Aching Beauty can
mask, which means that no minion can mask, since the only minion
with that Aching Beauty is the acting minion.