Quote from CatParty »Let's say Guardian of the Guildpact is being blocked by a green creature with 3 power; the damage will be prevented by Guardian's protection. So what happens if I cast Test of Faith before damage is declared - does the ToF prevent the damage and add the counters before Guardian's own protection prevents the damage? Or does the green creature not actually deal damage to the Guardian due to its protection?
702.16b A permanent or player with protection can’t be targeted by spells with the stated quality and can’t be targeted by abilities from a source with the stated quality.
702.16f Attacking creatures with protection can’t be blocked by creatures that have the stated quality.
616. Interaction of Replacement and/or Prevention Effects
616.1. If two or more replacement and/or prevention effects are attempting to modify the way an event affects an object or player, the affected object’s controller (or its owner if it has no controller) or the affected player chooses one to apply, following the steps listed below. If two or more players have to make these choices at the same time, choices are made in APNAP order (see rule 101.4).
616.1a If any of the replacement and/or prevention effects are self-replacement effects (see rule 614.15), one of them must be chosen. If not, proceed to rule 616.1b.
616.1b If any of the replacement and/or prevention effects would modify under whose control an object would enter the battlefield, one of them must be chosen. If not, proceed to rule 616.1c.
616.1c If any of the replacement and/or prevention effects would cause an object to become a copy of another object as it enters the battlefield, one of them must be chosen. If not, proceed to rule 616.1d.
616.1d Any of the applicable replacement and/or prevention effects may be chosen.
616.1e Once the chosen effect has been applied, this process is repeated (taking into account only replacement or prevention effects that would now be applicable) until there are no more left to apply.
616.1f While following the steps in 616.1a–d, one replacement or prevention effect may apply to an event, and another may apply to an event contained within the first event. In this case, the second effect can’t be chosen until after the first effect has been chosen.
Quote from CatParty »I guess I just don't know the fine print of protection, I know it prevents damage, but is the damage "dealt"?
615.1a Effects that use the word “prevent” are prevention effects. Prevention effects use “prevent” to indicate what damage will not be dealt.
615.6. If damage that would be dealt is prevented, it never happens. A modified event may occur instead, which may in turn trigger abilities. Note that the modified event may contain instructions that can’t be carried out, in which case the impossible instruction is simply ignored.
702.16e Any damage that would be dealt by sources that have the stated quality to a permanent or player with protection is prevented.