I run an Orzhov Aristocrats deck on MTGO and had something resolve in a way that made me realize I don't totally understand Protection or Triggering...
My board had a bunch of creatures including Blood Artist and Cartel Aristocrat when my opponent cast Damnation... so I started to sac' out my board before it could resolve, using Cartel Aristocrat's ability and triggering a bunch of drains with my Blood Artist, but at the end of my stack of triggers I set Cartel's ability to be Protection from Black... but she still died to Damnation? Was this a MTGO error or is that just how it works? Also if I hadn't made Artist my final sac', draining for 1 to itself dying, could I have left it and Cartel on the board and gotten 2 drain instead? Or does something about Damnation not activate the drain ability? I can't tell because it only wiped Cartel off the board with no Artist's around. My deck also runs a Geralf's Messenger and I'm wondering if Undying constitutes regenerating as mentioned on Damnation.
Damaged by sources with the specified quality. (All such damage is prevented.)
Enchanted or equipped by permanents with the specified quality.
Blocked by creatures with the specified quality.
Targeted by spells with the specified quality, or by abilities from sources of that quality.
Protection does 4 distinct, but specific things. It prevents:
Damage being done to the permanent with protection by a source with the stated quality. Enchanting/Equipping a permanent with something with the stated quality Blocking a creature with protection with someone with the stated quality Targeting the permanent with protection with something with the stated quality
You'll notice that Damnation does none of those (destroying is not the same thing as damage) so Protection from black doesn't work against it.
As to your second question: yes, you would have gotten 2 drain triggers. If you had just left your battlefield alone and let everything die at the same time, Blood Artist would have seen everything die along with it so every creature dying (including the Blood Artist) would have given you a trigger. There wasn't a need to sac your board in this case.
Regarding Messenger: Magic is an exceptionally literal game. If it does not say Regeneration (which Messenger does not) then it is not Regeneration. Regeneration and Undying are different abilities and Damnation will not stop Undying from triggering.
My board had a bunch of creatures including Blood Artist and Cartel Aristocrat when my opponent cast Damnation... so I started to sac' out my board before it could resolve, using Cartel Aristocrat's ability and triggering a bunch of drains with my Blood Artist, but at the end of my stack of triggers I set Cartel's ability to be Protection from Black... but she still died to Damnation? Was this a MTGO error or is that just how it works? Also if I hadn't made Artist my final sac', draining for 1 to itself dying, could I have left it and Cartel on the board and gotten 2 drain instead? Or does something about Damnation not activate the drain ability? I can't tell because it only wiped Cartel off the board with no Artist's around. My deck also runs a Geralf's Messenger and I'm wondering if Undying constitutes regenerating as mentioned on Damnation.
Thanks all
Damaged by sources with the specified quality. (All such damage is prevented.)
Enchanted or equipped by permanents with the specified quality.
Blocked by creatures with the specified quality.
Targeted by spells with the specified quality, or by abilities from sources of that quality.
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Damnation will still destroy Cartel Aristocrat.
And yes, you could have kept Blood Artist in play to drain an additional life.
Last but not least, undying is different from regeneration.
Damage being done to the permanent with protection by a source with the stated quality.
Enchanting/Equipping a permanent with something with the stated quality
Blocking a creature with protection with someone with the stated quality
Targeting the permanent with protection with something with the stated quality
You'll notice that Damnation does none of those (destroying is not the same thing as damage) so Protection from black doesn't work against it.
As to your second question: yes, you would have gotten 2 drain triggers. If you had just left your battlefield alone and let everything die at the same time, Blood Artist would have seen everything die along with it so every creature dying (including the Blood Artist) would have given you a trigger. There wasn't a need to sac your board in this case.
Regarding Messenger: Magic is an exceptionally literal game. If it does not say Regeneration (which Messenger does not) then it is not Regeneration. Regeneration and Undying are different abilities and Damnation will not stop Undying from triggering.