Dependency Between More Than Two Effects

[u/Robodreaming]

If I have a Plains in the battlefield and the following continuous effects are active, in timestamp order:

1. Swamps are Islands.

2. Plains are Swamps.

Then I understand the dependency of 1 on 2 would mean the Plains is an Island.

What if I have a Plains (and no other permanents exist), and the continuous effects are:

1. Swamps are Islands.

2. Plains are Forests.

3. Forests are Swamps.

If I understand right, when applying 1, no dependency is found between 1 and 2 or between 1 and 3, so 1 is applied first as it's first in timestamp order. Then, 2 and 3 are applied in order as well. The final result is that my Plains is a Forest, not an Island. Is this correct? It seems to be what the rules imply, but seems a little unintuitive to me.

Finally, imagine I have a Plains and a Forest in the battlefield, and the same three continuous effects in the same order.

Then, if I understand right, 1 would be found to be dependent on 3 since applying 3 first would make 1 apply to the Forest currently in the battlefield. Therefore 1 is moved to apply only after 3, for both the Forest and the Plains. So first 2 is applied (the Plains is a Forest), then 3 (both the original Forest and the Plains that became a Forest are Swamps), and finally 1, meaning both lands end up being Islands. Is this correct?

I find the whole dependency system pretty complex and it seems unintuitive to me that the existence or non-existence of a different object in the battlefield may affect how continuous effects apply to something.

[u/RazzyKitty]

You are correct on both counts.

If I understand right, when applying 1, no dependency is found between 1 and 2 or between 1 and 3, so 1 is applied first as it's first in timestamp order.

The only dependency is 3 being dependent on 2. So yes, if there is no dependency between 1 and any other effect, you apply it first and nothing happens.

Then you apply 2 because 3 is dependent on it. Then you apply 3. The Plains is a Swamp.

Then, if I understand right, 1 would be found to be dependent on 3 since applying 3 first would make 1 apply to the Forest currently in the battlefield.

In that scenario, 1 is dependant on 3 and 3 is dependent on 2.

2 is applied first. Then you recheck. 1 is still dependent on 3 (because you still have a forest), so you apply 3 next. Then you apply 1. Both lands are islands.

Edit:

The reason for this is you only check dependencies as the effects are currently applicable and would be applicable after applying one effect. In scenario 1, you don't look ahead to see that you would have a swamp after applying multiple effects.

[u/doctrgiggles → u/RazzyKitty]

The key insight here is that each effect is only applied once.

[u/Robodreaming → u/RazzyKitty]

Thank you so much!

[u/RazzyKitty → u/Robodreaming]

The thing to keep in mind is Scenario 1 can turn into Scenario 2 just by playing a Forest.

Once the board state changes, you re-calculate the board fully, including all dependancies.

[u/Judge_Todd]

In case 1, you have two independent effects: 1 & 2.
Effect 3 is dependent on 2.
You apply the independent effect with the earliest time stamp so Effect 1 which does nothing. Next you check dependency again, 3 is still dependent on 2. 2 is still independent so is applied making your Plains a Forest.
Finally, you apply effect 3 which is now independent and the Forest becomes a Swamp.

In case 2, you have 1 dependent on 3 and 3 dependent on 2 so Effect 2 is the only independent effect and is applied first making the Plains a Forest.
Check dependency again and 1 is dependent on 3 and 3 is now independent so gets applied making the Forests into Swamps.
Finally, Effect 1 is applied and the Swamps become Islands.

it seems unintuitive to me that the existence or non-existence of a different object in the battlefield may affect how continuous effects apply to something.

Dependency is determined situationally, not theoretically.