CPR 615.8 says:

Some prevention effects generated by the resolution of a spell or ability refer to the next time a specific source would deal damage. These effects prevent the next instance of damage from that source, regardless of how much damage that is. Once an instance of damage from that source has been prevented, any subsequent instances of damage that would be dealt by that source are dealt normally.

What is an “instance”?

Example: Pestilence is activated one time. I activate Jade Monolith to redirect the damage from my creature to me, so Pestilence is about to deal me – what? Two times (=“instances” of) 1 damage or 2 damage (in one “instance”)? How often do I have to activate my Circle of Protection: Black to prevent the 2 damage?

Thanks,

Mario Haßler

One activation will prevent all the damage.

The number of instances of damage is the number of times the verb “to deal” is used. Pestilence's ability says “Pestilence deals 1 damage to each creature and each player” - the verb “deals” is present only once, so all that damage is simultaneous and is one instance. Damage redirection effects don't modify the number of instances of damage - they just modify the recipients. So after applying Jade Monolith's replacement effect, you're being dealt 2 damage by Pestilence. The 2 damage will be prevented by a single activation of Circle of Protection: Black.

Daniel Kitachewsky
L3, Paris, France
Rules NetRep