I found this scenario in a forum and i think it's interesting and worth discussing:

Let's say my opponent is attacking me with Quillspike and Taunting Elf with an active Devoted Druid also on the battlefield, meaning he can, at instant speed, grow his Quillspike “infinitely”.

Meanwhile, I can't block it because of the taunting elf, but I do have an active Seeker of Skybreak equipped with a Runed Stalactite and a Judge of Currents on the battlefield, meaning I can, at instant speed, gain an “infinite” amount of life in one life increments.

So, he can announce making his Quillspike into 1 000 020 and I can announce gaining 1 000 000 life, to which he can respond to by growing his Quillspike, to which I can respond by gaining life etc.

How does this situation become resolved?

Increasing one's life is an advancement in game state, but to me the end result is:

A's proposed shortcut: I pimp my Quillspike to bring lethal damage.
N's proposed shortcut: I gain life to bring my life at your Quillspike's size plus 20

I believe this is a loop by the book even if life of one player grows (because the end state of each recursion of the loop is N will be at 20 life after combat and should be resolved by rule 716.3:

716.3. Sometimes a loop can be fragmented, meaning that each player involved in the loop performs an independent action that results in the same game state being reached multiple times. If that happens, the active player (or, if the active player is not involved in the loop, the first player in turn order who is involved) must then make a different game choice so the loop does not continue.

What do you think?

Edited Andrea Mondani (April 11, 2014 06:51:35 AM)

I think you nailed it spot on. There is an abstract loop of
a) ‘make my creature leathal’
b) ‘make my life > your creatures power’
goto a)

present, that involves choices, so active player will need to break the loop.

I agree with Philip (and with you). This is one of those examples where players are doing something that we have policy and documentation for, but unknowingly. Applying the knowledge we have about what they are doing is fine, here.

AP will need to break this ‘loop’.

Jack Doyle
L2, London, UK.

To add to Jack and Phillip…

I believe there would be ample cause to give the Quillspike Player a
Warning for Slow Play here as well since they are not advancing the game
state in a meaningful way. The philosophy in Slow Play also allows for
simply a caution and education, though further attempts at repeating the
loop multiple times could lead to an investigation for Stalling.

George, why do you say that? The scenario as Andrea posted it says “player A can do X,” not “player A does X”. Certainly this would be a case of slow play if player A just kept applying his loop shortcut, and player N called a judge on it, but what if both players were genuinely confused by how to proceed and called you over to ask about it?

I read the scenario as “This is what happened” instead of a player saying
“What if this happened?” Then obviously I'm not going to Slow Play them for
that.