Apologies if this is obvious or has already been asked. I couldn't find anything.
Estrid's Invocation's ruling says, "Once Estrid’s Invocation returns, it’s considered a new object with no relation to the object that it was. You must choose an enchantment that’s currently on the battlefield to copy (or to not copy anything). Auras that were attached to it will be put into their owners’ graveyards. Any counters that were on it cease to exist."
I assumed that meant that it returns to the battlefield either as a copy of something on the battlefield when it returns, or as an uncopied Estrid's Invocation without the ability. But then I was ready Legacy Enchantress stuff and people were talking about "free" Elephant Grass if you stack the triggers the right way. Does that mean that you can let the first Elephant Grass die, and you can keep exiling the copy and returning it as the Elephant Grass copy without paying the cost? Or does it indeed lose its Elephant Grass identity when it's exiled and returns. Maybe they meant that you get a "free" one if you keep paying the cumulative upkeep of the original Elephant Grass. I find this card very confusing.
If you're referring to the interation between Estrid's Invocation and Elephant Grass, here's how this scenario works:
Assume you control and own Estrid's Invocation that's a copy of Elephant Grass. It thus has "cumulative upkeep 1" and "At the beginning of your upkeep, you may exile this enchantment. If you do, return it to the battlefield under your control", among other abilities. Assume you also control the original Elephant Grass.
Your upkeep begins. Both abilities just mentioned trigger at the same time, as well as the original Elephant Grass's cumulative upkeep ability.
Then those abilities go on the stack at the same time, in the order of your choice. You put the cumulative upkeep abilities below the "At the beginning of your upkeep, you may exile..." ability.
All players pass, then the "At the beginning of your upkeep, you may exile..." ability resolves. You choose to exile Estrid's Invocation and return it to the battlefield under your control. Because the new Estrid's Invocation is different from the one that left as far as the game is concerned (C.R. 400.7), you may choose to have it enter as a copy of any enchantment you control, not just the original Elephant Grass. Assume in what follows that you choose to have it enter as a copy of the original Elephant Grass.
All players pass, then the old Estrid's-Invocation-turned-Elephant-Grass's cumulative upkeep ability resolves. You can't put an age counter on that permanent because it has already left the battlefield. You choose not to pay 1 for each age counter on the permanent, so you would sacrifice the permanent, which you also can't do.
All players pass, then the original Elephant Grass's cumulative upkeep ability resolves. You put an age counter on Elephant Grass. Then you must sacrifice Elephant Grass unless you pay 1 for each age counter on it.
EDIT: Numbered the steps after comment 3 was posted.
Great, thanks so much. Am I correct, then, that when the Estrid's Invocation is exiled and comes back, it's no longer an Elephant Grass? For instance, if you were unable or unwilling to pay the original Elephant Grass's cumulative upkeep cost and sacrifice it, the following upkeep your Estrid's Invocation wouldn't be able to come back as an Elephant Grass.
The interaction is essentially that you get a *2nd* Elephant Grass, one that you don't have to pay for cumulative upkeep for, but only if you keep the original around, so there's no interaction that gives you an Elephant Grass without a cumulative upkeep.
Is there some favorable interaction with Solitary Confinement? There's no real benefit of stacking them, so I'm unclear on what the favorable interaction is if my understanding of the Estrid's Invocation/Elephant Grass-style upkeep trigger interaction is correct.
Great, thanks so much. Am I correct, then, that when the Estrid's Invocation is exiled and comes back, it's no longer an Elephant Grass? For instance, if you were unable or unwilling to pay the original Elephant Grass's cumulative upkeep cost and sacrifice it, the following upkeep your Estrid's Invocation wouldn't be able to come back as an Elephant Grass.
The new Estrid's Invocation won't necessarily enter as a copy of whatever the old Estrid's Invocation was a copy of, if any. This is because the new permanent has "no memory of, or relation to, its previous existence" as the old permanent (C.R. 400.7).
Is there some favorable interaction with Solitary Confinement? There's no real benefit of stacking them, so I'm unclear on what the favorable interaction is if my understanding of the Estrid's Invocation/Elephant Grass-style upkeep trigger interaction is correct.
In the case of Solitary Confinement, the scenario is largely similar to the case of Elephant Grass, as given in comment 2. In the analogue to step 5, you can choose not to discard a card when the upkeep ability of the old Estrid's-Invocation-turned-Solitary-Confinement resolves, and you won't sacrifice that permanent because it has already left the battlefield.
Estrid's Invocation's ruling says, "Once Estrid’s Invocation returns, it’s considered a new object with no relation to the object that it was. You must choose an enchantment that’s currently on the battlefield to copy (or to not copy anything). Auras that were attached to it will be put into their owners’ graveyards. Any counters that were on it cease to exist."
I assumed that meant that it returns to the battlefield either as a copy of something on the battlefield when it returns, or as an uncopied Estrid's Invocation without the ability. But then I was ready Legacy Enchantress stuff and people were talking about "free" Elephant Grass if you stack the triggers the right way. Does that mean that you can let the first Elephant Grass die, and you can keep exiling the copy and returning it as the Elephant Grass copy without paying the cost? Or does it indeed lose its Elephant Grass identity when it's exiled and returns. Maybe they meant that you get a "free" one if you keep paying the cumulative upkeep of the original Elephant Grass. I find this card very confusing.
http://www.mtgsalvation.com/forums/the-game/legacy-type-1-5/661941-list-of-stores-that-support-legacy
http://www.mtgthesource.com/forums/showthread.php?28892-Compilation-Of-Legacy-Streams
EDIT: Numbered the steps after comment 3 was posted.
The interaction is essentially that you get a *2nd* Elephant Grass, one that you don't have to pay for cumulative upkeep for, but only if you keep the original around, so there's no interaction that gives you an Elephant Grass without a cumulative upkeep.
Is there some favorable interaction with Solitary Confinement? There's no real benefit of stacking them, so I'm unclear on what the favorable interaction is if my understanding of the Estrid's Invocation/Elephant Grass-style upkeep trigger interaction is correct.
http://www.mtgsalvation.com/forums/the-game/legacy-type-1-5/661941-list-of-stores-that-support-legacy
http://www.mtgthesource.com/forums/showthread.php?28892-Compilation-Of-Legacy-Streams
In the case of Solitary Confinement, the scenario is largely similar to the case of Elephant Grass, as given in comment 2. In the analogue to step 5, you can choose not to discard a card when the upkeep ability of the old Estrid's-Invocation-turned-Solitary-Confinement resolves, and you won't sacrifice that permanent because it has already left the battlefield.