Shadow Word: Death
There are enough decks that beat you with an early large minion (Big Priest with Eternal Servitude, Spell Hunter with Barnes into Y'shaarj, Cubelock with Mountain Giant, etc.) that you need an immediate answer sometimes, and you can't rely on Twilight Acolyte plus another dragon to be consistent.
See above. It’s still good. I didn’t change my mind.
Duskbreaker probably doesn’t need much explanation. It’s AoE on a stick and it challenges most meta decks’ power turns.
Priest of the Feast
This may seem odd given how few spells are in the deck, but you usually don’t need to heal for a ton off the card text; the threat of healing up to full in perpetuity is enough for your opponent to direct their damage at it. As a result, if it doesn’t get answered with hard removal, it basically heals you for 6 just by hitting the board. This also gives you a proactive play in slower matchups; tempo Priest of the Feast is a reasonable play in slower matchups. The health is relevant for Void Ripper as well.
Greater Healing Potion
Sometimes you just need to heal for 12 in a hurry. Other times you need to heal a minion for 12 in a hurry, so that you can flip it with Voidlord for extra burst. (And you thought that just because it can't target your opponent that it can't be used for lethal!)
Shadow Word: Horror
One of your primary board clears, Horror is best for removing high health or shielded minions, or combining with Pint Sized Potion and Potion of Madness to steal and remove a minion with deathrattle or potential to be resurrected on your side of the board instead of your opponent's.
Like Duskbreaker, this is just a card that’s too good not to play. Most of the situations you play this card are obvious, but don’t underestimate the value of information it gives you in terms of what exact archetype you’re playing against if you’re playing against Priest or Warlock. Knowing if you’re up against a Spiteful, Control or Combo Priest is really important for how you plan out your turns and line up your answers.
Cabal Shadow Priest
A 4/5 that steals minions and has tons of supporting cards to get minions into range is one of the main reasons you’re playing control priest. If you’re against a deck that doesn’t have must-steal targets like Rin and Voidlord, playing this without the battlecry as a tempo play can be fine.
Primordial Drake is effectively the death blow against Paladin; it removes a board of small minions awaiting a buff while also putting up a huge taunt that they likely won’t be able to deal with easily outside of Tarim or Equality. The 8 health also becomes a lot of burst in conjunction with Void Ripper.
Anduin is played primarily for the AoE Shadow Word Death effect, but it’s also very useful in a deck like this for whittling down your opponent’s health total for the last few points of damage. It's not a win condition on its own like it was in pre-nerf Raza Priest, but one challenge Priest decks can have is closing out games, and Anduin gives you that capability.
Seven dragons is the statistical sweet spot for consistently activating your other dragon battlecries, and it just so happens that the 12 health on Ysera generates a lot of burst with Void Ripper, especially in conjunction with Nightmare and Ysera Awakens. Dream can be clutch to get taunts out of the way or remove problematic minions stolen with Potion of Madness, and Ysera can also generate other dragons to activate future abilities. ￼
You need a third steal effect to effectively combat Control Warlock, and this does very nicely.
Priest of the Feast is the flex spot in the list. If you’re finding you’re seeing a lot of Cubelock and Secret Mage, you can try switching that out for an Acidic Swamp Ooze or a Gluttonous Ooze. (Don’t put in Harrison Jones, though; this deck often operates with a lot of cards in hand and Harrison can be slow and awkward to play.)
The epics (Shadow Visions, Twilight Acolyte, Primordial Drake, Dragonfire Potion, Cabal Shadow Priest and Void Ripper) are all core to the deck and shouldn’t be substituted. Unfortunately, control decks tend to run expensive and this is no exception, but those cards all work together in tandem and the rest of the deck revolves around those cards.
The legendaries, however, can reasonably be swapped out. If you don’t have Ysera, either Alexstrasza or Sleepy Dragon could be a reasonable replacement, and you can sub in either a second Dragonfire Potion or just a Shadow Word Death For Anduin. Zola the Gorgon could get some work done if you have it as well.
"This Looks Great, But Have You Considered...?"
Shadow Word: Pain
This list looks like it doesn't have enough removal; you need to play it to believe that it does. Pain really only becomes relevant for minions with exactly 3 attack, because you have tools to deal cleanly with anything smaller.
Elise the Trailblazer
Playing Elise is effectively conceding that you're going to win in fatigue most of the time, because it's really difficult to play the Un'goro Pack before you've made sufficient room in your hand to get adequate value from it. I've played enough games with Elise in the list to decide that the ability didn't provide value often enough to justify an understatted minion who's not a dragon in the list. I feel that Ysera is the best endgame card for this deck because it's a dragon, so it activates the other synergy cards early on, and it also has 12 health for Void Ripper lethals. Elise is more fun, though; I'll give her that.
Medivh, the Guardian
You just don't run enough big spells for Medivh to matter, he doesn't affect the board the turn he's played, and he's not a dragon. When I've tried Medivh it's almost always felt like win more in this specific list.
In general, your gameplan with this deck is resource exhaustion, and Psychic Scream works counter to that. Psychic Scream is great when you don't have any other good way of dealing with awkward to clear minions or powerful deathrattles, but the way this deck is built, you just steal those minions and move on with your day.
Primordial Drake has taunt, it has a bigger butt than Book Wyrm, and it clears a wave of Silver Hand Recruits singlehandedly. There are arguments for Book Wyrm depending on what you're facing, but your win rate against Dude Paladin will suffer dramatically if you swap out Primordial Drakes for them.
This was in the last version of the deck but it ultimately ended up being slow and dead in the hand a lot, and you have plenty of clears but not enough targeted removal; I swapped it out for a single Shadow Word: Death as I saw more mirrors, Combo Priests and Cubelocks playing Mountain Giants.
Always hold Northshire Cleric, Pint-Sized Potion, Netherspite Historian (even without a dragon) and Duskbreaker.
Against aggro, keep Potion of Madness and Shadow Word: Horror. If you have Duskbreaker and you’re on the coin, it’s ok to keep another dragon with it to ensure an activator but otherwise don’t.
Against control, keep Drakonid Operative, and keep Cabal Shadow Priest if you have Pint-Size Potion already.
Control - Favored
This is the reason you’re playing this deck. Control Priest wrecks slow Warlocks. Your general plan in this matchup is to ensure that Voidlord and Rin don’t get resurrected. Keep Pint Sized Potion in your hand at all times and be sure you can either Pint-Sized or Twilight Acolyte into Cabal Shadow Priest or Potion of Madness plus a board clear to kill those cards on your side of the board. Good Warlock players will recognize this is your strategy and will Dark Pact their priority minions proactively; this is fine for Voidlord, because you can just take the next one. The way you lose this matchup is an early Rin that dies on their end of the board; if that happens, pressure and draw as much as you can; they may be able to play one Seal a turn but you shouldn’t let them speedrun to Azari. Outside of that, though, they rely on the swing turns of N’zoth and Gul’Dan to win, and if you can defuse those, you can usually outvalue them in the endgame, because they’re going to go to fatigue long before you do.
Cubelock - Slightly Favored
This plays out similar to control except that you're worried about Mountain Giants and Doomguards instead of Rin. What you're trying to do is steal the Voidlords and kill the Doomguards on sight. The sooner you kill the Doomguards, the fewer of them they can make, and the Doomguards only come back once, but the Voidlords come back twice, so stealing one Voidlord is like killing 3 of them. If you're seeing a parade of Cubelocks it's reasonable to swap out the Priest of the Feast for a Gluttonous Ooze. This makes it much more difficult for them to execute the Cube plan, and significantly lowers their overall damage output.