If I'm playing a demon of pestilence, and my opponent has 8LP
And I have enough mana to pay the demon's ability the 8 times I need to kill him, the last 2 abilities on the stack would get resolved or not, because of the demon who is the source of the damage isn't on the battlefield because is dead. But that's what I think and I'm not sure about that, could someone help me please?
This should be in the Rulings forum and please use card tags:
Pestilence Demon (Since there is no "Demon of Pestilence", I assume this is what you mean)
Once an ability is on the stack, it exists independently of its source. Even if the source is gone, the damage is still dealt. It will do so using "Last Known Information" about the source. A clearer example might be Mogg Fanatic. Obviously the ability works but it is gone before the ability resolves. The same can happen here with the Demon and the damage will still be dealt.
That is assuming your opponent is not in the state of killing you*
In your example, if your opponent is in lethal range of your pestilence demon activations, and you activate it enough times to kill them, even if they kill the demon in response to any of those activations, the abilities are already on the stack and they will die.
But if you yourself somehow died, everything you've contributed to the stack are gone. For example if you have less life than that opponent, you will die on the resolution of one of the many pestilence demon activations before your opponent.
There are other effects that may come up here like split second cards that are needed to resolve before more activations, or time stop effects that may disrupt the stack. But those are not too commonly seen.
And I have enough mana to pay the demon's ability the 8 times I need to kill him, the last 2 abilities on the stack would get resolved or not, because of the demon who is the source of the damage isn't on the battlefield because is dead. But that's what I think and I'm not sure about that, could someone help me please?
Pestilence Demon (Since there is no "Demon of Pestilence", I assume this is what you mean)
Once an ability is on the stack, it exists independently of its source. Even if the source is gone, the damage is still dealt. It will do so using "Last Known Information" about the source. A clearer example might be Mogg Fanatic. Obviously the ability works but it is gone before the ability resolves. The same can happen here with the Demon and the damage will still be dealt.
In your example, if your opponent is in lethal range of your pestilence demon activations, and you activate it enough times to kill them, even if they kill the demon in response to any of those activations, the abilities are already on the stack and they will die.
But if you yourself somehow died, everything you've contributed to the stack are gone. For example if you have less life than that opponent, you will die on the resolution of one of the many pestilence demon activations before your opponent.
Killing opponents is the best counterspell.
There are other effects that may come up here like split second cards that are needed to resolve before more activations, or time stop effects that may disrupt the stack. But those are not too commonly seen.
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