WARNING: BEFORE LOOKING AT THIS DECK, FOLLOW THIS LINK TO VASTLY IMPROVE YOUR VIEWING EXPERIENCE ---> http://endlessvideo.com/watch?v=kVpv8-5XWOI
Now then, sit back, relax, enjoy the music, take a look at the deck, and have a good day. Suggestions and criticism are more than welcome, and I'll be more than happy to take a look at one of your decks if you would like me to. However, don't bother just posting your deck link by itself and expect me to follow it. I try to offer the absolute best advice and suggestions to every deck I take a look at (just look at my past comments). Now then, onto the deck:
If you have not figured this out yet, this is a deck known as Soul Sisters. The cards that give this deck its name, Soul Warden and Soul's Attendant happen to be very potent--more potent than a lot of people might expect in the Modern Format. Because Modern is generally creature based--as opposed to Legacy or Vintage where essentially every deck is either dedicated to some sort of intricate combo or to stopping it's opponent's combos--Soul Warden and Soul's Attendant provide a ridiculous amount of life.
One great combo in this deck is between Phyrexian Metamorph and Leonin Relic-Warder. Copy Relic-Warder with the Metamorph, then use the "enters the battlefield" ability to remove the Metamorph. This then returns the Metamorph to play, and you again copy the Relic-Warder and once again remove the Metamorph. This creates an infinite number of creatures entering the battlefield, which generates you infinite life, which makes your creatures better.
Here's a bit of an overview of how this deck does against other Modern decks, you can skip over this if you really don't care about it, but if you're interested in how Soul Sisters matches up against the competition, take a look:
1. Splinter Twin/Deceiver Exarch Combo Decks ---> One of the main reasons to play this deck is this specific match-up. Soul Sisters happens to essentially hard-counter one of the most effective Modern combo decks, Deceiver Exarch/Splinter Twin. Every time they copy their Exarch, you gain 1 life, meaning that their onslaught of 10,000,000 Deceiver Exarchs will result in you gaining 10,000,000 life, then taking 10,000,000 damage putting your life total exactly where it was before. Plus, if you have a Soul Sister and Ajani's Pridemate out, you get a 10,000,002/10,000,002 creature out (have fun fitting those counters onto your card). You still need to be careful and you don't really want them to start the combo (for fear that they might make all their Exarchs bigger of something), but this deck is absolutely great against this deck whether it is RUG or RUB.
2. Melira Pod/Project Melira/Whatever else it is called ---> Some Soul Sisters decks lack the removal you want to stop Melira Pod, but this deck has a nice removal suite of cards, ranging from Fiend Hunter and Path to Exile for Melira or you can just Obilivion Ring their Pod. There's a decent amount of removal, you should be able to stop them before they combo out.
3. Literally any type of Aggro Deck ---> I do not care what type of aggro deck you are playing; RDW, Zoo, whatever you have, it does not matter. You will lose. Especially when you're on the play, a turn 1 Soul Sister essentially means that their Wild Nacatl or Goblin Guide is going to be swinging for one less and each creature they play or that you play makes you harder and harder to kill. Once you get beyond the really aggressive stage of the game, your Serra Ascendants, Ajani's Pridemates, and other creatures will overpower and eventually steamroll them. I still like to sideboard in a Kor Firewalker against RDW and other red based aggro decks just because it makes winning even easier.
4. Any deck with Dark Confidant ---> Never remove a Dark Confidant. Your opponent casting a Turn 2 Dark Confidant can actually be a semi-good thing (yeah I can't believe I just typed that either). One thing that Soul Sisters does better than just about any other deck in Modern is delaying the game. Therefore, when your opponent has a Dark Confidant out, Bob starts ticking away at his life total a lot faster than he's taking away your life, and you'll win a long drawn out grind. So many decks play Bob that your ridiculous ability delay becomes one of your most powerful aspects when you play this deck.
5. Faeries and other aggro-control decks can be a bit tougher than the regular aggro decks, but the later you push the game the better chance you have at winning. If you ever get to or beyond 30 Health your Serra Ascendants will win you the game easily.
6. Storm/other crazy combo decks ---> Against combo decks like Storm I generally sideboard in 4 Thalias in place of Fiend Hunters and Path to Exile. You can generally stay alive against Storm decks, but it's still something you should watch out for. Against Grapeshot decks the extra bit of life you've gained yourself should keep you alive and against Empty the Warrens decks, the burst of life you gain combined with Serra Ascendants and Ajani's Pridemates should give you killing blows in the few turns following.
7. I have not really played against Delver decks, but I would imagine that playing against Delver would be a bit like Faeries except less Control elements and more Aggro, which happens to be what this deck is better against.