The latest iteration of my ETB-stifling jank deck, now for Historic!

Hushbringer and Strict Proctor turn off/tax ETB effects, which in addition to disrupting many decktypes, allows you to disregard the drawbacks of Kroxa, Acererak, and Clackbridge Troll when they enter the battlefield. Being able to beat face as well as force discards/summon tokens/trample through blockers can often be too overwhelming for an opponent to handle, especially if their own plans are shut down. I recommend mulliganing hard for either Hushbringer or Strict Proctor in your opening hand.

The rest of the deck can easily vary around the core of these 5 cards, depending on the matchups you're facing. Reidane's front half can be great for delaying board clears that would otherwise ruin your day, while the back half can help stymie removal or aggro. Cleansing Nova sometimes arrives too late to be useful, but makes up for it with versatility against artifact or Nine Lives decks. I really love Containment Priest, as it shuts down the Minion of the Mighty combo, reanimators, Collected Company, and Muxxus. It's also great for surprising aggressive 1/1s as a bonus. 

Strongest matchup: Lifegain, absolutely. GW is a bit tougher than mono-W, but almost the entire deck turns to dust in the face of one of your ETB stiflers.

Weakest matchup: Auras. They quickly outpace your beaters and never run out of steam. Vanishing Verse might be a strong sideboard card if you take this to bo3, but I've never not struggled against that deck. If you see a Lurrus companion, I recommend mulliganing hard for an early removal spell (I'm using Heartless Act at the moment, but other options are valid).

HOW TO BEAT:
Lifegain: Play a stifler and watch their deck fall apart. Abiding Grace and non-ETB-based sources of lifegain can get around this, but can usually be beaten with sideboarded graveyard or enchantment hate. Containment Priest nullifies Abiding Grace and Cleric Class's resurrection effects.

Reanimator/Delver: Find a Containment Priest and hold onto it like your life depends on it, because it usually does. Soul-Guide Lantern is the second-best solution. Reidane can help delay spell-based reanimation.

Goblins: Stiflers shut down tempo cards like Wily Goblin, Goblin Instigator, and the ETB effect of Muxxus. You'll still want removal for haste-givers and Muxxus itself. It's a tough matchup, but it's winnable if you can get a beater down early.

Elves: Stiflers can slow them down but rarely stop them. Cleansing Nova will usually be needed; sideboard in cheaper clears like Ritual of Soot or Shatter the Sky if applicable.

Slivers: Stiflers don't do all that much, but flying can help stem the bleeding. Instant-speed spot removal will usually be needed to turn a crucial combat in your favor, First Sliver usually locks you out and there's nothing to be done about it.

Mono-brown ramp: Very difficult matchup. Reidane slows down most of the key cards, Kambal punishes their early ramp plays (especially on the play), but if you can't Cleansing Nova their board on curve, you'll usually be in trouble. Abrade is an excellent sideboard or even mainboard card if you see a lot of these.

Enchantments: Kambal can do big work in this matchup, usually you can just wait for a Cleansing Nova to turn up. Alternately, Kroxa's life-loss/discard efffect can slowly kill your opponent around Nine Lives/Solemnity.

Izzet Phoenix: Kambal to punish all the noncreature spells (or at least eat a burn spell), Containment Priest to delete any Arclight Phoenix trying to return (or at least eat a burn spell).

Azorius/Jeskai Control: Space out copies of a stifler/beater combo to dodge board clear, land Reidane if you can to slow them down. Sideboard in Storm's Wrath or similar to try and burn down planeswalkers.

Neoform Combo: Play a stifler and/or hold a Containment Priest to turn off their combo. Get multiple stiflers out if you can, as they're usually equipped to bounce or burn one at end of your turn.

Niv-Mizzet: Expect Lightning Helix to be available on turn 2 and hold stiflers accordingly to block Niv-Mizzet's ETB effect. You want to try and keep one on the board as they hit 5 mana and force them to be inefficient with their removal.

General tips:

Lotus Field synergizes well with Strict Proctor, if you encounter a lot of land destruction.

Dungeon Descent is a good way to use your Kroxa, Reidane, Acererak, or Kambal on an otherwise stalled board.

If you have 4+ mana open and Proctor rather than Hushbringer out, when you play Kroxa, you want to pay for the FIRST trigger (forcing the discard) and decline to pay for the second one (the sac effect).

Proctor taxes landfall effects, which can be easy to forget. Ruin a Ruin Crab's day.

If you want to leave Clackbridge Troll as a blocker without giving the opponent the chance to tap it, play it postcombat.

If the board is stalled, it's absolutely valid to play Acererak without a stifler to power through dungeon rooms for value.