In Magic the Gathering, What does protection from creatures mean?

Answer 1

Protection in Magic: The Gathering was originally introduced with protections from colors. The four things that go along with protection from color (or artifacts) are:

1) Damage of that color that is dealt to the creature or artifact with Protection is prevented (I believe this is a change from the original function which was that it was reduced to zero)
2) Enchantments or Equipment of the color (or artifact) Protected against on the creature fall off. Enchantments go to the graveyard, and equipment falls off as it does. This generally only happens if a creature or an artifact acquires protection sometime after it is cast, because enchantments or equipment couldn't get on the creature otherwise by #4.
3) Blocking the creature with a creature of the Protection color is not possible. For example, a White Knight (which has Protection from Black) cannot be blocked by any black creature.
4) Targeting the creature with spells or effects of the Protected color is not possible. For example, you could not target a Black Knight (with protection from white) with Swords to Plowshares, because it is a targeted effect. But, un-targeted effects work fine (so a Black Knight would go to the graveyard because of Wrath of God -- it does not do damage, and it is not targeted)

The acronym to help you remember these is DEBT -- Damage, Equip/Enchant, Block, Target.

In later sets, the designers have become more creative with "Protection from" mechanisms and have extended them out to more specific instances, such as artifacts, creatures, and specific creature type (e.g. "Protection from Goblins, Protection from Kavu, Protection from Beasts")

The net effect of having protection from creatures is:

1) Damage -- Damage received from creatures by the creature with Protection is prevented. The practical effect is that with Protection from Creatures, the creature with protection could block all day and not die from creature damage.
2) Equip/Enchant -- Not very applicable, as I can't think of any enchantment or auras that are creatures -- Opalescence only affects global enchantments (not auras), and I believe the working on the licid cycle says that they turn into an enchantment (and are no longer a creature)
3) Block -- A creature with Protection from Creatures could not be blocked by creatures.
4) Target -- A creature with Protection from Creatures could not be targeted by any creature generated effect (e.g. not targeted by Prodigal Sorcerer or Royal Assassin's abilities) Non-targeted effects are fine, so long as they are not damage (E.g. "When this creature goes to the graveyard, all creatures get -1/-1 until end of turn" is not a targeted ability, and it is not damage, so Protection does not Protect against it)

Two cards which have protection from creatures are Commander Eesha (from Judgment), and Beloved Chaplain.

Answer 2

Mtg Protection From Creatures

Answer 3

First off, remember that creatures are not attacked by other creatures - the player is attacked by creatures. However, if you assign a blocker with protection from red to block a red creature (or red-black, red-green, etc), it will take no damage. Consider it protection from red + any other color... Now, if the red creature has trample, some of that damage will still roll over to the player.

Answer 4

Works the same as any other protection ability. Just creatures instead of colors.