MTG Salvation

Curio's trigger uses the stack. Normally, when you trigger an ability like Curio's, it's taken for granted that you will "pass priority" - that is, see if your opponent has any responses and if he doesn't, the ability immediately resolves. The magic words are "hold priority" - this means that you're going to activate another ability while one of your abilities is still on the stack.

Example: You have 2 untapped Elves and Curio. You cast Heritage Druid. Announce, "I'm going to activate Curio's trigger. I hold priority." The Curio trigger doesn't resolve yet, so you can use Heritage Druid to tap three Elves for mana. Once that is done, you allow the Curio trigger to resolve and bounce an Elf.

I'm new to the game, but want to play Elves, can someone tell me how you're able to use Heritage Druid to respond to the triggering of Cloudstone Curio? Onlone I'm told "awesome combo" in the real world I'm told "can't respond with Heritage Druid, too late, you have to do them one at a time, not together", :/

This deck wants its finishers to cost only green or colorless mana, because the mana engine (Heritage Druid) only produces green. Grapeshot was playable in Extended (during PT Berlin) because Birchlore Rangers let you generate red even off summoning sick Elves.

Ezuri would be the ideal finisher in situations where you don't have an infinite combo going. You can hold out one turn by using untapped Elves to block, tapping them for mana with Heritage Druid, then regenerating the blockers with Ezuri. Fortunately for this deck, Storm and Eggs are gone, so there are fewer scenarios where you die despite having lots of blockers.

I still hate the Storm and Eggs bannings, though.

With this sort of combo deck, you need every single mana source available when you combo off. You can't just go "eh, I'll hold back an untapped Stomping Ground". Sooner or later you'll run low on mana and be forced to tap it for green, just to cast an Elf and keep the combo going.

Seeing as this deck works by casting more elves to combo off, would it not be reasonable to splash red for a storm finisher? Grapeshot being my favored choice?

If a forest was dropped for a stomping grounds it would still be fetchable.

Rubin: This deck doesn't need a Beck to combo off. Beck is terrible in multiples (1, you need a splash color to play it and 2, casting 2 Becks likely leaves you with 0 mana left to cast Elves), so I play only 3.

Trimonkey: It's the surer thing. Ezuri beatdown can be ruined by Wrath of God (no regeneration). If you have the infinite mana combo running, it's not too hard to get the last piece for the infinite draw:
1) Have Beck//Call, Elvish Visionary or Regal Force in hand (and the mana to cast it)
2) Use Summoner's Pact or Primal Command to tutor for Visionary/Force.
3) Use Eternal Witness to bring back a Visionary/Pact/etc from the graveyard.
If you want to play the 4th Curio you should probably cut a Deathrite Shaman/Boreal Druid for it, not Command.

drtravian: My gut feeling is that Beck is not strong enough to provide this deck with the same amount of resilience as the Extended version. The Modern version is much more vulnerable to removal. We'll have to see if it performs well on MTGO or at GPs.
With regards to SBing, I would try using one similar to Affinity's. Stuff like Relic of Progenitus, Grafdigger's Cage, Dismember, Spell Pierce and Unified Will would make good inclusions. Fecundity and Lead the Stampede help you survive board wipes.
Don't just copy the Nass SB; the meta was different then. Jitte and Dark Depths don't exist in Modern, so you can't play Jittes of your own and Ghost Quarter is not effective. I'm also hesitant about splashing white, because previous experience with splashing a third color in Storm and Eggs (for Channel the Suns and Wargate, respectively) didn't lead anywhere.

Have you done any proxy testing? How do you think it holds up against the current (and projected) meta?

Any sideboard suggestions? anything changed since since posting?

How did your testing go, Trimonkey?

I really like your list. I think I'm going to throw this together for some testing today. One thing though, I am going to cut the Primal Command (maybe for the fourth Cloudstone Curio, but I'll have to test and see). It just feels like a win more. Your example requires you to have both infinite mana and infinite card draw (I understand it can be done without the card draw, but that requires it to be naturally drawn since the deck contains no tutors for it). Given you have infinite mana and infinite draw, and assuming one of your creatures does not have summoning sickness (which is very likely), you can just kill them on the spot with Ezuri (a second creature without summoning sickness even plays around Path to Exile) or gain infinite life off of Essence Warden to survive until your next untap. Aside from that I really like all of your explanations for the combos. This deck seems like a fun one.

Running less than 4 beck//call is insanity.