I had an interesting debate with my local L2 about shortcuts and what determines if one is acceptable. From my understanding, the complexity does not necessarily matter, as long as you can describe a loop and all outcomes of each iteration, with a proposed end state. So my argument, which stemmed from my own Krark-Clan Ironworks Eggs deck that he was playing last night, is this:

If I have a board state consisting of Darksteel Citadel, Codex Shredder, Chromatic Star, Krark-Clan Ironworks, and Lotus Bloom, with a Faith's Reward in hand, can I propose a loop that is the following:

Tap, sac Darksteel Citadel, use Lotus Bloom's ability for white, sac Chromatic Star, draw a card, sac Krark-Clan Ironworks, cast Faith's reward, use Codex Shredder's ability to get Faith's Reward back and repeat.

This “combo” nets one colorless mana, or one white mana, and one draw per iteration. Say I propose an end point of “I draw X cards and have X mana floating, where X is the number of cards in my library.” I then would cast another Faith's reward, using four white mana that I had floating, and would sacrifice the Lotus bloom to get me three red, so that I could cast Banefire for what would most likely be lethal.

Is this an acceptable loop? I personally feel like this is fine, as there is a clear loop to repeat, a clear ending point and a clear board-state afterward.

Another side note, is there any limit as to what is not acceptable? From reading the Comprehensive rules and the MTR, I couldn't discern a clear definition of acceptable versus not acceptable. I understand that this is much more complicated than something like Splinter Twin plus Pestermite, but to me the end state is just as simple.

Edited Ryan Wood (April 7, 2015 09:06:32 PM)

To be able to perform a loop like this, you need to be able to tell us two things: how many iterations will it take to get to your desired game state, and what will the game state look like when the loop is over. This combo seems fine, because you know how many iterations it will take to get to the end (X, where X is the number of cards in your library), and you know what the game state will be (I will have those permanents on the battlefield, X mana in my mana pool, and the cards that were in my library in my hand).

Nathan Long

Edited Nathan Long (April 7, 2015 09:13:22 PM)

Originally posted by Nathan Long:

is there any limit as to what is not acceptable?

As implied by Nathan's answer, it's not an acceptable “loop” when you have a variable element that makes it impossible to state an exact number of iterations.

The example of this that gets argued the most (I think I've answered the question, in one form or another, a few dozen times over the years…): a series of actions that results in milling card(s) from an opponent's library, but that opponent had the foresight to add Gaea's Blessing or Emrakul, the Aeons Torn in their deck.

And, without fail, someone wants to argue that they can “loop” until the shuffler is the only card left in the library. After all, it's a *near* certainty that it will happen, eventually! But no, you can't state how many iterations it will take, and there's still that infinitesimally small chance it won't happen in your lifetime, so, no, you can't shortcut to that outcome. Obviously, they're disappointed; I just smile and say Stifle.

d:^D