Mulligans
General Mulligans
Mulligans are pretty easy for this deck: you want Sketchy Information, as well as cards that can help you draw it.
Aggro Mulligans
Against aggro I would keep removal, especially cards that can kill Trogg. It's tricky, though, because against druid you don't know if they are aggro or ramp.
Control Mulligans
Against control decks I felt comfortable keeping the Illusionist, especially against Blood DK. You can afford the slower start against that deck.
This is a deathrattle rogue deck built around using Scourge Illusionist, Masked Reveler, and Forsaken Lieutenant to copy Invincible, or to copy each other for a steady supply of discounted cards that give you more cards. I just hit legend with it today with a 75% win rate (72w 24l) from bronze. It is a ton of fun to play, and it felt either dominant or competitive in every matchup. I didn’t encounter a mirror even once, so it doesn’t seem like many people are playing this archetype.
The idea is to tutor for the Illusionist with Sketchy Information, which gets you a discounted Reveler or a discounted Invincible. When the Reveler dies, it can hit the Illusionist, Invincible, or Forsaken Lieutenant, the latter of which can be used to copy the same Illusionist you drew off Sketchy. This continues the chain, giving you a steady supply of 4/4 rushers or 4/4 Invincibles. The deck typically wins games by building a massive minion with Invincible. Snowfall Graveyard is absolutely bananas with Invincible’s deathrattle. I had multiple games where I swung for lethal with a 20+ power minion on turn 6 or 7.
Everything the Reveler can pull is a great target for one of your copies of Invincible. Even the lieutenant: though you lose the battlecry buff, you get two Invincibles that buff each other on death. Against board-based decks, this is usually game-over. Killing one just buffs the other, and the taunt protects the 5/1 you get from reborn. They have to get through more like 20 health in total if they don’t have silence.
Besides that, the deck just runs a bunch of spells. Gone Fishin' and Door of Shadows can help you draw key cards like Sketchy Information. Other than that, I lean heavily on direct damage because you often want to be killing your own minions. Serrated Bone Spike and Preparation make for a nice trick that lets you play minions early, if you are unlucky and draw Invincible for example.
I was using the deathrattle sword for a while but it just felt way too slow. It would usually sit in my hand as a dead card. I’ve been trying out Potion Belt, but Reconnaissance also makes sense in that slot. I don’t have a copy of Shadow of Demise, but I have to assume it’s very good in this deck.
Matchups
The deck is very strong against control/value decks. I absolutely slaughtered Blood DK with it, which might account for my winrate because I matched against so many of them. Ramp druid also felt favorable. Miracle rogue was competitive and seemed to come down to luck of the draw. If I landed an early double-Invincible or if they had a slow start I would win. Frost DK and Shockspitter Hunter were trickier because they can burn you even if you get a taunt from Invincible. Aggro druid was also tough, in part because I never knew whether to mulligan for ramp or for aggro. You want totally different cards in those two matchups, with the single exception of Sketchy Information.
In general the deck is good against control, as well board-based midrange decks, because the our Revelers can clean up their board and enemy minions give us easy ways to trigger our deathrattles.
Only one deck felt like an auto-lose: thief priest, which I only encountered once. They could silence my deathrattles to slow me down and they had so many steal effects and deathrattle synergies that they could use my cards better than I could. It was a really funny game.
The deck is obviously weak against mass silence, but frankly I don’t think even two copies of the starfish can save Blood DKs from this deck. The matchup just seemed so one-sided.