Do creatures that enter the battlefield at the same time see each other enter?

Question

Let's say I have Goldnight Commander on the board. He is a 2/2 that says:

Whenever another creature enters the battlefield under your control, creatures you control get +1/+1 until end of turn.

I play a Thatcher Revolt. It says:

Put three 1/1 red Human creature tokens with haste onto the battlefield. Sacrifice those tokens at the beginning of the next end step.

The sacrifice portion is not important to this question. What is important is how these two cards interact with each other.

Playing this card in my first main phase, assuming no counters or other shenanigans by my opponent, I will have my Commander and 3 tokens on the battlefield. What will happen in terms of the power/toughness of my tokens and Commander?

Option A

The tokens will be 1/1 each. They don't see each other come in at all. The Commander is 3/3, as one "enter the battlefield" trigger happens.

Option B

The tokens will be 1/1. They don't see each other come in at all, because they weren't on the battlefield to see any of the triggers. The Commander is 5/5, as he saw three "enter the battlefield" triggers occur.

Option C

The tokens will all be different, with one being 3/3 as he saw the other two come in, one being 2/2 as he saw only the last one come in, and 1/1 as the last one saw none come in.

Option D

The tokens will all be 4/4, as three creatures entered the battlefield this turn.

I am obviously hoping for this option. It may be supported by a ruling on Goldnight Commander that says, emphasis mine:

The creature that entered the battlefield will also get +1/+1 until end of turn if it's still on the battlefield when the ability resolves.

The key being the ability resolving. So my thought is thus:

• Thatcher Revolt goes on the stack.
• Thatcher Revolt resolves, and three separate "enter the battlefield" triggers go on the stack as the three humans enter the battlefield as 1/1.
• The last (it is a stack) "etb" trigger resolves. This puts an ability from Goldnight Commander on the stack. This resolves and the humans are now all 2/2.
• The next "etb" trigger resolves. This puts a new ability from Commander on the stack, and resolves with the humans being 3/3.
• The first "etb" trigger finally resolves, puts a Command ability on the stack, which resolves putting the humans at their final state of 4/4.

Option E

The tokens will all be 2/2.

• Thatcher Revolt goes on the stack.
• Thatcher Revolt resolves, and one single "enter the battlefield" trigger goes on the stack.
• The "etb" trigger resolves. This puts an ability from Goldnight Commander on the stack. This resolves and the humans are now all 2/2.

I would really like to have a complete understanding both of the result and how this result is calculated by the game engine.

Answer 1

Summary: Option D is spot on. All three of your 1/1 are now 4/4 until end of turn (and your Commander is 5/5 until end of turn).

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The question has nothing to do with whether the tokens see each other enter the battlefield or not.* It's about how many creatures are on the battlefield when each of the triggered abilities resolve.

The game unrolls as follows, starting with Thatcher Revolt's resolution:

1. Thatcher Revolt places three creatures on the battlefield simultaneously. Goldnight Commander's ability triggers three times. [CR 603.2][CR 603.2c]
2. As a player is about to receive priority, you place Goldnight Commander's ability on the stack three times. [CR 603.3]
3. The third instance of Goldnight Commander's ability resolves: Creatures you control get +1/+1 until end of turn.
4. The second instance of Goldnight Commander's ability resolves: Creatures you control get +1/+1 until end of turn.
5. The first instance of Goldnight Commander's ability resolves: Creatures you control get +1/+1 until end of turn.

Three continuous effects were created by a triggered ability. They will only affect the creatures that existed when the abilities resolved [CR 611.2c], but all three of the 1/1s were on the battlefield when they resolved.

So all three of your 1/1 are now 4/4 until end of turn (and your Commander is 5/5 until end of turn).

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* — To answer your title question, yes. If you had two creatures with a triggered ability such as "When another creature enters the battlefield, ...", they would see each other entering the battlefield. This is codified by CR 603.6d: "Normally, objects that exist immediately after an event are checked to see if the event matched any trigger conditions. [...]"

For example, if two Goldnight Commander entered the battlefield simultaneously, both of their abilities would trigger [CR 603.6d], and both would end up getting +2/+2 until end of turn.

Answer 2

The answer to this situation is D, since it is a triggered ability.

More generally, when multiple permanents enter the battlefield simultaneously, abilities behave as follows:

Replacement effects (As [this permanent] enters the battlefield, You may have [this permanent] enter the battlefield as..., and [This permanent] enters the battlefield with) will look at the state of the battlefield before the group of permanents enters.

Triggered abilities (When [a permanent with certain characteristics] enters the battlefield) will trigger for all eligible permanents in the group entering the battlefield. This is true even if the ability is on one of the permanents that is entering the battlefield.

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Examples

If you use Scapeshift to find several copies of Valakut, the Molten Pinnacle, some mountains, and several copies of Vesuva, you will have a group of lands entering the battlefield simultaneously. Vesuva's ability is a replacement effect, and so can only copy lands on the battlefield before the group of lands enters (so if you sacrificed all of your lands to Scapeshift, Vesuva would only be able to copy an opponent's land). Meanwhile, Valakut has a triggered ability. All of the Valakut abilities will trigger for all of the mountains entering the battlefield. If the Valakuts happen to be mountains as well, such as due to Prismatic Omen, they will trigger their own and each others abilities.

If you use Living Death, any instances of Clone that come back to life will have no valid copy targets and Canker Abomination will be a 6/6, since both of these are replacement effects. Meanwhile, Goldnight Commander has a triggered ability, and so will give all of your creatures +1/+1 until end of turn for each creature besides himself that entered the battlefield.

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Rules Justification

The behavior of the triggered abilities comes from the following core rules:

603.6a Enters-the-battlefield abilities trigger when a permanent enters the battlefield. These are written, "When [this object] enters the battlefield, ..." or "Whenever a [type] enters the battlefield, ..." Each time an event puts one or more permanents onto the battlefield, all permanents on the battlefield (including the newcomers) are checked for any enters-the-battlefield triggers that match the event.

603.3b If multiple abilities have triggered since the last time a player received priority, each player, in APNAP order, puts triggered abilities he or she controls on the stack in any order he or she chooses. (See rule 101.4.) Then the game once again checks for and resolves state-based actions until none are performed, then abilities that triggered during this process go on the stack. This process repeats until no new state-based actions are performed and no abilities trigger. Then the appropriate player gets priority.

The behavior of the replacement effects comes from the following core rules:

608.2g If an effect requires information from the game (such as the number of creatures on the battlefield), the answer is determined only once, when the effect is applied

614.1c Effects that read "[This permanent] enters the battlefield with ... ," "As [this permanent] enters the battlefield ... ," or "[This permanent] enters the battlefield as ... " are replacement effects.

614.12. Some replacement effects modify how a permanent enters the battlefield. (See rules 614.1c–d.) Such effects may come from the permanent itself if they affect only that permanent (as opposed to a general subset of permanents that includes it). They may also come from other sources. To determine which replacement effects apply and how they apply, check the characteristics of the permanent as it would exist on the battlefield, taking into account replacement effects that have already modified how it enters the battlefield (see rule 616.1), continuous effects generated by the resolution of spells or abilities that changed the permanent’s characteristics on the stack (see rule 400.7a), and continuous effects from the permanent’s own static abilities, but ignoring continuous effects from any other source that would affect it.

614.12a If a replacement effect that modifies how a permanent enters the battlefield requires a choice, that choice is made before the permanent enters the battlefield.

614.4. Replacement effects must exist before the appropriate event occurs—they can’t “go back in time” and change something that’s already happened. Spells or abilities that generate these effects are often cast or activated in response to whatever would produce the event and thus resolve before that event would occur.

101.4. If multiple players would make choices and/or take actions at the same time, the active player (the player whose turn it is) makes any choices required, then the next player in turn order (usually the player seated to the active player’s left) makes any choices required, followed by the remaining nonactive players in turn order. Then the actions happen simultaneously. This rule is often referred to as the “Active Player, Nonactive Player (APNAP) order” rule.

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Note:

This question is currently the canonical question for how to handle multiple permanents entering the battlefield simultaneously. This answer is intentionally more general than the question is looking for, in order to address the numerous variations of this question.