This deck is all about the undead synergies. Let your units die to buff Ilmire Rot Eater/trigger Harvester coundowns, create Revenants from Anima Condiuts.
Prepare yourself to get used to losing units. Early game is all about setting up your side of the board for mid game - getting chump blockers out, and scrolls that will benefit from them dying. Mid game, you want to focus on reducing your countdowns so your units will attack more often, and take down opponent blocking units. Late game you're looking to wipe your opponent's row clean and take out idols by posiitoning your Irva where your undead units will trigger her attack effect. It's important to know what to sacrifice, and when. Be mindful of which stage of the game you're in and sacrifice anything that doesn't help the current phase you're in.
I try to control when my creatures will die with this one. Try not to start losing units until you'll benefit from doing so.
An ideal first hand will have a 1 drop, two 2 drops and an Ilmire Rot Eater 3 drop, surrounded by your 1 cost cards. Not only does this give you a big board presence, but it sets you up to play this deck as it should. Mire Shamblers on a one drop are a bit risky, as they are suceptible to a Hasty Wolf, or anything that will attack before you. If I get a Slayer Vestige out, I like to protect it with my Rot Eater, but anything else that comes out in the first few turns, I use as a meat sheild for buffing the Rot eater. A buffed up Rot eater is good at taking out Sheilds and armored units. Use Languid in this early phase to protect your creatures from dying before you're ready for them to.
Scrolls that benefit from a creature dying:
Harvester - counts down when ANY creature dies on either side.
Ilmire Rot Eater - buffs health and attach when an adjacent creature of yours dies.
Anima Conduit - spawns a Revenant when a creature on your side dies.
Soul Scrounger - (enchantment) unit will countdown when ANY creature is destoryed (yours or theirs)
Loyal Darkling - Only benefits from itself dying, by damaging your opponent's idol on the same row by 2. If you have to lose someone before you have one of the above scrolls out, this is arguably the best unit to lose.
It's preferable if you get at least one of the above mentioned scrolls out before you let something on your side die. Ultimately, you want to have multiple scrolls out that benefit from something dying to give your presence a lot of value. However, you have to strike a balance of getting the beneficial scrolls out, with playing sacrificial scrolls. If you have to lose a scroll, I'd rather it be a 1 cost Husk or Mire Shambler than an Anima Conduit (who's gift will keep on giving over several turns). An example of this is to play two chump blockers a turn prior to dropping your Anima Conduit in the back row, even if you lose a chump before then. It's better than placing your conduit out in the open where it will become a target.
After you have your Rot Eater, blockers, and an (both would be even better!) it's time to think about getting a Harvester and or an Anima Conduit out. If you can get your Harvester out before killing an opponent creature, that's to your benefit, too. Make use of Languid, to prevent your opponent from killing your units before you're ready for them to die.
WARNING: Here's the big risk of playing this deck. If you didn't get your early game setup right, and start losing weak units before you're ready to, you could find yourself trying to keep up with dropping chump blockers, and losing the resource game. It's imperative that you get your early game base established first, even if it takes a bit longer than expected.
If you can get your Rot Eater in front of an anima conduit, which chump blockers in front of him, and a Harvester in a back row behind your sacrificial blockers, you're in a good position to let your opponent kill some chumps. The Rot eater will grow fast, and your Harvester will count down fast, especially if you have Anima Conduit out! I try to keep a Slayer or two near the back row, but will use them as chumps if I have nothing else to perform that duty. If you can use them to at leat kill one other unit before losing them as a chump, you'll maximize your per-scroll value.
Now it's time to think about reducing your countdowns. Undead creatures are slow.
Scrolls to control Countdown:
Flesh Animator- reduces all undead units (yours and theirs!!) countdown by 1, when his countdown is zero.
Restless Bones - Reduce UNDEAD countdown by 1 (and increase their attack by 2 this turn!)
Soul Scrounger - countdown is reduced by 1 any time (yours or theirs) creatures are killed.
Shroud of Unlife - This doesn't control countdown directly, but will make any creature "Undead" which can be triggered by Flesh Animator, and Restless Bones, so I'm including it here. Think of putting this on your Harvester to double countdown speed, Flesh Animator, to affect most of your board, or on your Rot Eater, to swing big, often.
I like Shroud of Unlife mainly to make other creatures "undead", which can drop their countdowns triggered by Restless Bones, and the Flesh Animator. the added bonus that a Husk will be spawned in it's place when it dies is a huge added bonus. This scroll can also be used strategically, to make a creature who's about to attack undead. This is mainly important for triggering Irva's effect of delivering two ranged attack when an undead crature deals damage. Now, almost every creature in your deck can be "undead"
On the subject of countdowns, Soul Scrounger can go nicely on your Harvester (to double it's countdown speed) but I've found it very useful on my Flesh Animator, too. You might find your Decay deck attacking as often as an aggro Growth deck with this combo.
Late game is all about Irva. She shouldn't really come out until you're ready for her to. Read her text carfully, and learn how to use her wisely. She sends a ranged attack of 2 anytime an Undead creature deals damage to another unit. She'll make four attacks of 2 each, when your Harvester kills 3 units and damages an idol. If that's not enough, she'll add an attack of her own when she counts down. So it's important to get your undead creatures attacking, to use Irva's ability wisely. Leverage your countdown control scrolls to maximize Irva's potential. Pay close attention to her positioning on the board, as well as the undead creatures who are attacking, so you can time all the attacks right.
Your opponent will try to target your Harvesters, Irva, Rot Eaters, Flesh Animatores and Anima Conduits for removal. I've included Sanctuary of the Lost for this reason. Naturally this only covers Harvesters, but you can use Shroud of Unlife on your non Undead creatures to offer some protection under this.
Sometimes I run this deck wihout Loyal Darklings, but they are too good to be true. They make great sacrificial creatures. Nothing is more satisfying than winning a match by sacrificing a loyal darking when your opponent carfully stacked blockers in front of a weak idol.
Let me know how you play this, or would change it up.