This was my first thought when I saw Kobold Illusionist revealed. At first, you just see a mish-mash of removal and Legendaries. Yet once you explore Hearthstone mechanics, you can truly see the beauty of the deck.
If you’re playing against an Aggro deck, you want board clear. Thalnos plus Fan of Knives would be the best, but grabbing a Shiv could work as well. The deck is full of board clears though, so it’s a decent matchup.
If against a control deck, the combo is your best friend. Grab Spiritsinger Umbra and two Kobold Illusionists. Generally they won’t be able to deal with a bunch of Dreadsteed-wannabes, so you can just keep pinging away at whatever they drop. If you can’t get them, card draw is also your friend.
You want to try to get Spiritsinger Umbra as well as two Kobold Illusionists in your hand at the same time, with no other minions in hand and Malygos in your deck. Drop Spiritsinger and one of your Kobolds to fill your board with Kobolds. Then next turn, you trade away your Spiritsinger to make room for whatever minion you draw (so your board of Kobold Illusionists don’t summon non-Kobold Illusionists). Your infinite Kobolds should be enough coupled with your board clears to stall the game until Maly. Then once you draw Maly, drop the Kobold Illusionist from your hand, trade away your Illusionists to get 6 Malygos’s, then Shiv or Evis the opponent’s face for over 30 damage in one turn.
Side-note: Make SURE you save either an Evis or Shiv for the combo. Otherwise you just have a bunch of mini-Malygos’s and no spell to kill your opponent with. I guess you could bluff a Sinister Strike and get a free concede somewhere in there, but yeah.
TECHNICALLY it isn’t an OTK since you need preparation beforehand, but the deck really only gets countered by silence (which is rare besides Purify Priest) and bad draws (most notably drawing Maly too early, in which case you could make the deck Wild and put Gang Up in your deck to shuffle Maly back for your Spiritsinger combo to pop off). Is this a viable deck? Heck no. But it’s definitely going to be a ton of fun and will definitely get some clips on YouTube 😀
If you want to play this in Wild, I highly recommend putting in Gang Ups for more consistency, in case you draw Maly early, and maybe an Azure Drake or two for easy board clear spell damage as well as an easy card draw. Conceal could work as an alternate win-con, but the whole point of the deck is Kobold Illusionist, so meh. I wouldn’t like it.
Malygos and Spiritsinger Umbra are both essential to the deck. If you don’t have either of them, just play another deck. I guess you could run infinite Shadowcaster Factory with Brann to replace Umbra, but it’ll be a much more complex deck to completely combo.
Patches is there for cycle. You could replace it for Backstab I guess, but it’s great in basically any Rogue deck with Swashburglar.
Thalnos is specifically there for spell power, but the card draw is nice. Wild Pyromancer is probably a good tech vs Aggro, but any spell power or card draw can work in its place.
Valeera, the Hollow is simply a nice card to have. It can fill the board with Shadowcasters, double-up on board clears, and makes for a lot of fun and consistency. The deck does function without her though, so maybe a Sprint in her place to grab more card draw into your combo and board clears.
EDIT IN POST: It completely skipped my mind that Ragnaros could be used in place of Malygos for an alternate win-con. So in wild, I recommend swapping maybe an Si:7 or Shadowcaster for Rag. Or if you don’t have Maly, put Rag in instead. 48 damage randomly should be enough to OTK after picking off a couple stragglers with trading away your Kobolds.