As you are reading this article, you are probably a fan of Magic and are well aware that it can be a very complex game. While the rules of the game are extensive and cover a lot of ground, in most scenarios, very few rules are actually applied. It is usually the interaction between a few of these simple rules that gives Magic its complexity, not the entirety of the rules.
Below is a series of questions and answers from a player regarding just seven different cards from Magic. All of them are all relevant to a specific combo (Grindstone / Painter's Servant) and ways in which that combination can be foiled. Each situation only uses only four different cards at most, and two use multiple copies of the same card. These eight questions and their answers cover a lot of ground; including many aspects of triggered abilities, replacement effects, and infinite loops. Enjoy!
Q: I've got a few questions regarding Grindstone's interaction with cards like Painter's Servant. For all of these questions, assume I'm the player with the Painter's Servant / Grindstone combo. What happens if an opponent puts a Gaea's Blessing into his graveyard due to Grindstone?
A: Technically speaking, as the Gaea's Blessing is put into his graveyard, the Blessing's ability will trigger. (You can tell it is a triggered ability as it uses the word "when.") But it is not until after the Grindstone ability has completely resolved that Gaea's Blessing's triggered ability will go on the stack. When this trigger resolves, all cards that are currently in this graveyard will be shuffled into this player's library. This also means that the cards that are shuffled back into this library will not be milled again as the Grindstone ability has already resolved. Remember that triggered abilities do use the stack, so Gaea's Blessing's ability can be responded to by any player in the game.
Q. OK, so what happens if an opponent puts a Darksteel Colossus into his graveyard due to Grindstone?
A: Darksteel Colossus is a bit different. It does not have a triggered ability like Gaea's Blessing; its relevant ability is a static ability that generates a replacement effect. Replacement effects do not use the stack; they alter the application of some other action or event. As the Colossus would go to the graveyard from milling, it is instead shuffled back into its owner's library. This cannot be responded to like Gaea's Blessing's ability, as the Colossus' ability alters what happens when Grindstone's ability resolves. Because the Painter's Servant is in play this means that this individual Colossus card can end up being 'milled' over and over again, as it will be returned to the library before the next two cards are milled.
If there is only one Colossus in this library, that means that eventually the only card remaining in this library will be the lone Colossus. This is because the Colossus and some other card would be the last two cards in the library. They would both be milled and the Colossus would be shuffled back in by itself. As the last two cards did share a color due to the Painter's Servant the milling process would be repeated again. This time you'd just mill the Colossus and shuffle it back in. But because the Colossus was the only milled card it did not share a color with another card, so the resolution of the Grindstone's ability will end.
Q. What if the opponent has two copies of Darksteel Colossus in his library?
A: You just had to go there, didn't you? If there are two Colossi in the library, then as the Grindstone ability is resolving they will be milled with other cards and individually shuffled back into this library. Assuming that there are no other effects applied as the Grindstone ability is resolving, eventually the only two cards in the library will be the two Colossi. These two Colossi will then end up being milled, and shuffled back into this library over and over. This will cause this Grindstone ability to loop as it can never completely resolve. Anytime the game enters a mandatory loop that no player can break, then it is a draw. So this game will be over, no one actually won it, and you move on to the next game.
Q: What if I also have a Leyline of the Void in play and a Gaea's Blessing is 'milled' into my opponent's graveyard due to Grindstone?
A: When the Gaea's Blessing would go to its owner's graveyard, it will be removed from the game instead. This is because Leyline of the Void has a static ability that generates a replacement effect. (This works like Darksteel Colossus' ability, as the application of this effect does not use the stack.) When Grindstone's ability resolves the effect from the Leyline ability will change where the milled Blessing ends up. Because the Blessing does not actually go to a graveyard, its ability will not trigger.
Q: Replace the Gaea's Blessing with a Darksteel Colossus in the situation above: what if I have a Leyline of the Void and his Colossus is milled?
A: In this example we have two completing replacement effects that try to change where this milled Colossus ends up: the effect from the Leyline's ability and the one from the Colossus' own ability. Whenever something like this happens (two replacement effects both trying to alter the same event), the affected player or the controller of the affected object chooses to apply one of the effects first. Then if the other effect is still applicable it is applied. In this specific situation the owner of the Colossus would choose to have this 'milled' Colossus either be shuffled back into his library or to have it removed from the game. Regardless of what the player chooses, the Colossus is no longer going to its owner's graveyard, so the other effect is not applied. The "smart" choice for this player is to have the Colossus be shuffled back into his library, as this may keep him in the game a little bit longer.
Q:. Now add another Colossus. What happens if my opponent has two Darksteel Colossus in his library, I have Leyline of the Void and Painter's Servant in play, and activate Grindstone?
A: This situation is like the one above involving two Colossi up to a point; eventually there will only be the two Colossi in the library, but now you've introduced a choice into the loop. The player must choose the option of applying Darksteel Colossus's replacement effect first to continue the loop, so it's not a mandatory loop. After shortcutting a chosen number of iterations, that player must choose to apply Leyline of the Void's replacement effect first instead and end the loop by losing one or both Colossi forever, in which case we return to the sequence with one Colossus in the library or none.
Q: Ok, here's a little bit of a different track. What if a Gaea's Blesing is milled and I activate the ability of Tormod's Crypt targeting my opponent after Gaea's Blessing trigger ability has gone on the stack but before it resolves?
A: If there are not any cards in the graveyard to be shuffled back into the library when the Gaea's Blessing triggered ability resolves, then nothing will be shuffled back in. Assuming that you have milled your opponent's entire library with Grindstone, then your opponent will end up with an empty library, an empty graveyard and a lot of cards in the removed from game zone.
Q: What happens if an opponent puts Gaea's Blessing into his graveyard due to Grindstone and I play Extirpate targeting Gaea's Blessing before Gaea's Blessing trigger ability resolves?
A: Targeting a Gaea's Blessing with Extirpate will prevent that Gaea's Blessing, and other "found" copies of Gaea's Blessing from being shuffled back into the library. However, it will not prevent the Gaea's Blessing triggered ability from resolving. This means that all other cards in this graveyard will end up being shuffled back into its owner's library. It does not matter that the Gaea's Blessing itself will not be shuffled back in.
So in conclusion, the Painter's Servant / Grindstone combo has the ability to win, but there can be a few stumbling blocks in the way if your opponent is not cooperative. Understanding the difference between triggered abilities and static abilities with replacement effects, how and when replacement effects are applied and how triggered abilities work can help you pilot this combination.