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A: This doesn't work, for three reasons.
1) Regeneration only works when a permanent is destroyed, or dealt lethal damage. It's not possible to regenerate from a sacrifice, because it doesn't use the word "destroy".
2) If a permanent regenerates, it does so instead of leaving play. Disciple of the Vault will not trigger when an artifact regenerates.
3) Sacrificing Welding Jar is the cost to play its ability. Costs happen before effects, so the Jar will be in your graveyard long before anything is protected. Because of this, it's impossible for two Welding Jars to regenerate each other, or even to target each other at the same time. You can sacrifice them both if you want (you can have the second target itself if your really want to sacrifice it), but then when their abilities resolve, they won't find anything left to regenerate.
A: No, it doesn't. Changing a land into a basic land type causes it to lose all rules text in its text box, and this includes the ability that makes it indestructible.
It remains an artifact land, because Blood Moon only changes the land subtype and removes all rules text other than the ability to tap for red mana, it retains all the other card types it has, like artifact.
A: Yes, it is. The Twin token is an artifact creature that can be used for anything an artifact creature can be used for, and you are allowed to sacrifice it to something else before you are forced to sacrifice it at the end of combat.
-- David Mace
A: No, it doesn't. Memnarch only checks if the target is an artifact at two specific times – when the ability is activated, and when it resolves. Once the ability has resolved, you keep control of the creature, regardless of what form it has.
Q: Talon of Pain. Our local judge says that if you control 2 or more Talons and use one of them to deal damage then the others get counters. I disagree. The card says "Whenever a source you control other than Talon of Pain deals damage to an opponent, put a charge counter on Talon of Pain." I say it means any card named Talon of Pain. Which way is correct?
-- Tim Haywood
A: Your local judge is correct. When a card refers to its own name in its text, it refers only to itself. The clause "other than Talon of Pain" means "other than this card", other Talons of Pain will trigger it, and you can put counters on one Talon of Pain if another Talon of Pain deals damage.
Q: If you lose life while Lich's Tomb is in play and can't sacrifice a permanent what happens? Also if you're under zero life and this occurs what happens?
-- Justin Pellino
A: You will usually have a permanent to sacrifice – Lich's Tomb is also a permanent that can be sacrificed, and you must sacrifice it if there are no other permanents to sacrifice. With its effect not active anymore, you will lose the game if you are at zero of less life.
-- Gianluca Bevere
A: You can do this. Culling Scales targets a permanent with the lowest converted mana cost each of your upkeeps, and you are allowed to choose indestructible permanents even though they won't be destroyed by the effect.
A: No, it doesn't. Mycosynth Lattice only changes permanents in play to artifacts, cards not in play are just colorless, but not artifacts. Since the Engineer can only be used to pay for artifact spells and activated artifact abilities, it can't be used to pay for the colorless Mana Leak, it's not an artifact.
Q: If I play Machinate, will I be able to stack the cards that are put back?
-- Antonio Negron
A: Yes, you will. When multiple cards are put into the library at the same time, the owner of the library chooses the order they go into the library. You can put the cards in any order you like.
General/Older Card Questions
-- Stephan Ansey
A: You can do this. Nevinyrral's Disk is usually destroyed by its own effect, but if it has a regeneration shield, it won't be destroyed, it will be regenerated instead.
This is different from many similar cards, like Oblivion Stone, which says that you sacrifice it to pay the activation cost – it's not possible to regenerate something that is sacrificed, only things that are destroyed.
Q: I was wondering what happens when you animate equipment and then activate it targeting itself? In other words: what happens when I have a Skullclamp and Karn, Silver Golem in play, and play the activated ability of Karn targeting the Skullclamp, thereby making the Skullclamp a 1/1 artifact creature which retains its abilities, and following this up by activating the equip ability of Skullclamp targeting itself? Does the Skullclamp die, while checking for state-based effects? And if so do I get to draw 2 cards?
-- Maarten Jacobs
A: Equipment that is also a creature can't equip anything, so this trick won't work. You can activate the equip ability, trying to have Skullclamp equip itself when it's a creature, but rule 212.2i in the Comprehensive Rulebook says that this doesn't work, so the ability fails to do anything.
Also, if an equipment that is equipping a creature is turned into a creature, it immediately stops equipping the creature.
-- Shawn Gibson
A: You're exactly right. Sun Droplet's abilities are triggered abilities (you can tell, because triggered abilities begin with "When", "Whenever" or "At"). Triggered abilities are almost always cumulative.
When you're dealt 5 damage, all your Sun Droplets will see it, and all of them will trigger. They gain 5 counters each. And every turn, for the same reason, each one will gain you 1 life.
Q: I was playing a game with my friend and a question came up as to who is supposed to draw a card when Solemn Simulacrum goes to the graveyard. I gained control of my friend's Solemn Simulacrum via Confusion in the Ranks. Then I sacrificed the Simulacrum to my Atog. Do I (the current controller) draw the card or does my friend (the owner of Solemn) draw the card from Simulacrum's triggered ability?
-- Tony Wong
A: You draw the card. If an ability triggers when something leaves play, the game will look back in time to get details of what left play. It sees that Solumn Simulacrum was controlled by you, so you also control the triggered ability, and get to draw the card. It doesn't matter whose graveyard the Simulacrum goes to.
Q: What would happen if I had a Lifeline and a Mogg Bombers in play, and then put another Mogg Bombers into play?
Would it create a loop that would kill my opponent in the same turn the second Mogg Bombers came into play?
A: No, it wouldn't. Lifeline will put Mogg Bombers into play "at end of turn". This refers to a specific moment in the turn - the beginning of the end-of-turn step. You only have one end-of-turn step each turn.
So... the end-of-turn step begins, triggering Lifeline. Then, Lifeline's ability resolves and puts Mogg Bombers into play. Then, the other Bombers hurt your opponent and die. And finally, Lifeline says "return the Bombers to play at end of turn".
That effect won't happen until the beginning of an end-of-turn step, and there's only one of those each turn - so it's missed its chance this turn. The Bombers will come back into play at the end of the next turn.
So this is a loop, in a sense: but it only deals 3 damage per turn.
A: Null Brooch can be used with an empty hand. The act of discarding your hand just demands that you discard all cards in your hand and that the hand is empty afterwards, and this is satisfied even when you have no cards in hand.
This is different from discarding a card, as this event looks for a card to go from your hand to the graveyard.
Q: When my friend played Death Grasp, I said that I could use either Circle of Protection: Black or Circle of Protection: White to prevent the damage. He said that I had to use both to prevent the damage. I want to know if I have to use both, just one or if I can't use either to prevent damage.
A: You can use either of the Circles to prevent the damage. The damage dealt by Death Grasp is both white and black, and anything that can prevent white or black damage can prevent this damage.
Q: If I play Ertai's Meddling on a spell can I counter the spell when the last delay counter is removed, or then when there are still some delay counters?
-- Lauri Paakkari
A: You can only counter spells that are on the stack, so while the spell is removed from the game, it's not possible to target it with counterspells. You will have to wait until the last delay counter gets removed: the card will go back onto the stack, and wait to resolve like any other spell. You're free to counter it then.
-- Nathan Harmata
A: Yes, it does. Cloudpost's ability to come into play tapped is a replacement effect that modifies how it comes into play, regardless of how this happens. Cloudpost will always come into play tapped.
Q: With a Leonin Shikari in play, and you play multiple creatures on the same turn, is it possible to have them all attack with a Lightning Greaves in play? For example, if I play a Shikari and another Leonin Shikari on the same turn, can I equip Lightning Greaves to one, then during the declare attackers step, attack with it then still, during the declare attackers step, equip the Greaves to the other one, and attack with that?
A: This doesn't work. All attackers are declared at the same time, and you can't do anything between declaring individual attackers. Only one creature will be able to attack - the one equipped by Lightning Greaves when the declare attackers step begins.
A: It will be put in its owner's graveyard, as it will have 0 toughness. Cards with an X in its mana cost only know the value of X when the card is on the stack, In play or in other zones the X is considered to be zero, even if there are counters on the card. The converted mana cost of Chalice of the Void while in play is always zero, and it will be a 0/0 creature when animated by an effect.
A: Both creatures will die. Since both the legends have been in play for equal amounts of time, they are both affected by the Legend Rule (rule 420.5e in the Comprehensive Rulebook), and are both put into their owner's graveyard.
Q: Suppose that I have a Cathodion in play, and a Reshape in my hand. Can I sacrifice the Cathodion as the additional cost of playing Reshape, and use the mana I get from the Cathodion going to the graveyard to pay for the mana cost of Reshape?
-- Phil Berman
A: You can't do this. The ability from Cathodion goes on the stack like a regular triggered ability, and you won't get the mana until after Reshape is fully paid for – meaning that you can't use the Cathodion mana to pay for Reshape.
Q: When Gemini Engine puts a Twin token into play, is the Twin tapped or not? The card says the Twin is an attacking creature, but it wasn't there when attackers were declared so I don't think it would be tapped. This could come in handy with Lodestone Myr.
-- Marc Baker
A: The Twin comes into play untapped since it doesn't specifically say that it comes into play tapped. It comes into play attacking, but since this is after attackers have been declared and tapped, it will be an untapped attacker, much like a Serra Angel. You can tap it to pump a Lodestone Myr.
-- Chris Purington
A: You can put the modular counters on the Dreadnought. You sacrifice the creatures as part of the event that puts the Dreadnought into play, and the triggered ability goes on the stack the next time you get priority, which is after the card has come into play.
When you sacrifice creatures to the Dreadnought, the game sees their current power, including modifiers from counters, equipment and other effects.
A: Yes, it does. Maze of Ith has two effects – untapping the creature and preventing damage. As long as the targeted creature is attacking, the Maze's effect will do as much as possible, and even though untapping the creature doesn't do much, the damage prevention still happens.
Thanks to Laurie Cheers and Lee Sharpe for feedback and proofreading.