With each new set, I like to take a look at the cards to see how they function in multiplayer games. I'm looking for the card that gets an extra benefit in games with multiple players. Primeval Titan is a great card, but it doesn't get better with extra opponents. I want cards that go from good to great, or great to awesome, simply because there are more opponents.
Before we get into the cards themselves, I want to mention a couple of the keywords that behave a little differently in a multiplayer environment.
Exalted encourages you to attack with just one creature. As the number of creatures you control wth exalted grows, that single creature you're attacking with gets bigger and bigger. The merits of this in multiplayer games changes from one game to the next. If the single creature you are using to attack can be chumped by token creatures or smaller creatures that your opponents can play out each turn, then your plan isn't all that effective. With just a bit of evasion, things can be a lot better.
The true benefit of exalted with multiple opponents is that it encourages you to leave your army back to stand guard. When a creature is tapped to attack, it is unavailable to block against multiple opponents. In a one-on-one game, you trade the loss of a blocker for the damage that creature can inflict on the attack. That trade looks awfully sketchy when you have three opponents who are each taking a turn attacking you through your now vulnerable defenses. With exalted, most of your army stays back to block, but they still help the single creature you are sending in. Exalted pumps up your offense while keeping your defense strong.
Annihilator is the other keyword. I'm not mentioning it here to tell you how amazing it is, but to warn you of the difficulties coming your way. Let's use Artisan of Kozilek as the example. I see an opportunity and play Artisan of Kozilek, bringing a Kami of Ancient Law back to the battlefield from the graveyard. I pass my turn. On your turn, you look at your battlefield and realize that annihilator 2 may be coming your way. Or it may not. It completely depends on who I choose to attack. If I'm going to attack someone else, you're happy to see them sacrifice two permanents, but if I'm attacking you, you'd prefer to destroy the creature before that happens.
But annihilator doesn't work that way. You have to take your chances, or use up your removal. This means that if you are using creatures with annihilator, you need to take into consideration that every one of your opponents is likely working out a way to either kill you quickly or kill your creature.
Don't Do It
While the rest of this article is going to tell you about a bunch of great cards, I want to perform a public service and warn you against using a couple of cards. The first is Swans of Bryn Argoll. Swans appears to be a way to hit for 4 damage with a creature that is very difficult to kill off, but don't be fooled. In fact, it is a way for your opponents to draw plenty of cards. That 4 damage you are doing isn't close to enough damage to make up for the massive card disadvantage you are going to suffer from the Swans. Unless you are running the Swans as part of a combo package that lets you draw several cards, do not bother. There is always someone with a direct damage spell that is happy to do 5 or 25 points of damage to the Swans.
The second card I want to discourage you from playing is Iona, Shield of Emeria. This card will completely neuter at least one of your opponents, and possibly more, every time it comes out to play. Iona does nothing but destroy someone's good time, leaving them powerless while the game continues on around them. This card is just a nightmare for your playgroup. Do yourself and your playgroup a favor and take a pass on Iona.
Elesh Norn takes your deck of small and mid-sized creatures, and turns it into a wrecking crew. Your creatures become very difficult to kill and usually bring things to an end quickly. The real power with Elesh Norn is the -2/-2 to your opponents' creatures. This will kill off plenty of creatures, and leave the remaining too puny to truly handle your army. Your 2/2 flyer now trades with your opponent's 6/6 flyer. It really is just that good.
I've heard several players suggest that this is as bad as Iona, but I disagree. Iona protects herself by locking down the opponent who is best able to stop her. Elesh Norn has no such defenses. Anyone who has any creature removal can get rid of her and return the board to a more stable state. Elesh Norn can be miserable, but with a little preparation, she can also be handled.
Necrogenesis, along with its predecessor, Night Soil, are two cards I've used to great effect. Necrogenesis removes a creature card from any graveyard to give you a 1/1 Saproling token. Generally I see the token as a bit of a bonus, preferring to use Necrogenesis as a way to stop a lot of the endless recursion that tends to happen in multiplayer games. It is the rare game where no one is actively returning creatures from their graveyard to the battlefield, and Necrogenesis shuts that down. With multiple graveyards to choose from, you'll find yourself with an endless supply of Saproling tokens.
While I downplayed the importance of the token, it does add to the effectiveness of the card. You can activate the ability at instant speed, so you have access to a chump blocker some opponents won't consider, or another creature to sacrifice when an opponent thinks they can force you to sacrifice a more valuable creature.
Between Necrogenesis and Night Soil, Necrogenesis is the more difficult card to cast, demanding two colors. It is far more effective, however asking only one creature card in the graveyard. Night Soil requires two creature cards from the same graveyard. This can lead to some awkward situations when you are waiting for your opportunity to use Night Soil, and your opponent is happy to get their single creature from the graveyard.
All is Dust really is a "mass" removal spell. If you are running it in your black-red deck as a way to wipe the board, this is a great card. Not only does it get rid of all the creatures that most mass removal spells can do, but it also solves your enchantment and Planeswalker issues. It can even help with some artifacts, and seven colorless mana really isn't all that big a price to pay for a large board wipe.
Many players look at the card and refuse to run it in their decks since they don't want to lose all of their cards that have at least one color, but keep in mind you were losing all your creatures to Day of Judgment, and your permanents to Nevinyrral's Disk, so the downside for All is Dust isn't all that bad.
Admittedly, using All is Dust in your colorless deck turns it into an all-star that deals the crushing blow to your opponents. When your Nevinyrral's Disk hits everyone but you, then a single well-timed casting can bring games to a quick end.
Just a note: Painter's Servant gives all of your permanents a color. That was a painful lesson for me.
This Spirit offers nothing but upside with multiple opponents, taking out three opponents' creatures just as effectively as one. The card works slowly, but does put a countdown on your opponents' creatures, forcing a response. Unfortunately for them, attacking you isn't generally a great plan with a 5/5 creature with wither waiting to welcome them.
I should mention that the Doubling Season Rule only somewhat applies to Midnight Banshee. Since the counters are being put on creatures you don't control, Doubling Season is ineffective. Primal Vigor doesn't work here either, since we aren't putting +1/+1 counters on creatures. You'll ideally be looking at proliferate options to try and speed things up.
The key to effectively using this card is your ability to protect it and yourself. You'll need to be able to deal with removal since this card will rank high among creatures that need to be gone. While your Banshee will likely kill off an attacking creature, many opponents' strategies will be seriously compromised, so they'll be sending the works your way. You'll need to have plenty of defenses ready for the onslaught.
I believe you were looking for a way to protect yourself from an opponent's rush of creatures? All those creatures dying due to Midnight Banshee's upkeep ability are coming right back on to the battlefield, except this time they are fighting with your forces of darkness.
With more opponents, you'll get more creatures dying and coming under your control, so you'll have more creatures to use against them. As another wither creature it continues the Banshee's theme of rushing creatures off their mortal coil. If you are looking to run this without the Banshee, consider Black Sun's Zenith. As long as you don't kill off the Necroskitter with Black Sun's Zenith, you'll be getting every creature with three toughness or less on the battlefield under your control, along with all of their enter the battlefield triggers.
The joy of Puppeteer Clique is that it doesn't care which graveyard the creature card comes from. While you can build your deck to use Clique to best take advantage of your own creatures, having more graveyards only brings more options. Perhaps you have a way to eliminate an opponent's best creature? Follow up that play with a Puppeteer Clique and enjoy the benefits you were admiring only moments before!
I was thinking, Midnight Banshee will give you plenty of creature options in opponents' graveyards. Even in a deck with Necroskitter, the Clique will work. When an opponent's creature dies with a -1/-1 counter on it, the Necroskitter returns it to the battlefield under your control. When that creature dies, it ends up back in an opponent's graveyard. Necroskitter doesn't activate again since the creature was under your control, so it stays there. Now the Puppeteer Clique can jump in and give you a further one-turn use, all while helping to keep your opponents' graveyards uncluttered with less fortunate creatures.
The deck churns through opponents' graveyards rather effectively. Necrogenesis clears out the less desired creatures, giving you Saprolings to sacrifice to Culling the Weak to get the mana to play your more expensive spells. Deathrite Shaman is happy to use your opponents' graveyards for a variety of benefits as well. I've included Vulturous Zombie as well. I know that sort of goes in the face of the -1/-1 counter theme we have, but with so many creatures dying, hopefully repeatedly, the Zombie can become a creature opponents will want to deal with even more than the Midnight Banshee.
I hope you've enjoyed our romp through some of the multiplayer friendly cards in Modern Masters 2015 Edition. Let's do this again in a few months when Origins hits the scene!
 Admittedly, most creatures with annihilator are so good that your opponents were already looking at ways to kill your creature.
 The Doubling Season Rule states, "Any card that produces a token creature or counter will be made better by Doubling Season and other cards that double or add to your counter/token totals in some way."