I know they're a bit pricier than the $3-4 avg. the deck has, but I can't recommend Reconnaissance and Dolmen Gate enough (in addition to Iroas). Reconnaissance, if you aren't familiar, allows you to swing with literally everyone safely, untap each creature at the most opportune time, deal combat damage in most situations (ignore the 20+ year old reminder text, it's misleading), and have every one of those creatures untapped by the end of combat. Creatures are considered "attacking" until the end of combat step ends and you untap anyone who got through for combat damage as you move to that step.

Devilish Valet will 1 shot someone out of the game (or several someone's with the above effects out). 6 tokens entering makes him 64 power which is enough to get the job done... but hitting in the literal millions is very possible with this guy. I've hit for over 8 million damage personally and it felt good (23 tokens entering got me there).

Last_Laugh I'll consider the options in the long run. I just had a big upgrade in this deck so I'll be testing it out again.

Last_Laugh what would you consider removing?

Hoarding Ogre, Djeru and Hazoret, and Hellrider since it only hits one opponent are what I'd cut personally.

I'd also swap Adriana, Captain of the Guard for Skyhunter Strike Force. Same effect but 2 less mana and on an evasive creature.

Oh, feel free to check out my Isshin list for any other ideas. Upvotes on any of my decks are appreciated. EngrIsshin - All Your Base Are Belong to Us!

I'd actually keep Hellrider. Its Scryfall rules reminder states that Hellrider deals damage to the corresponding defending player or planeswalker each of those creatures is attacking.

I think you could swap out Phyrexian Dragon engine, mostly since it doesn't really help you much on its own, and Isshin doesn't necessarily want to be utilizing discard draw. I removed the Meld options from my Isshin deck in the past few months, mostly because the Meld opportunities happened 2-3 times in the two years I've been playing the deck.

I'd recommend checking out Professional Face-Breaker as a potential replacement, especially to compliment some of the other Treasure production you already have in your deck. I play her in Isshin and Prosper respectively. Her floor and ceiling are a bit different in each deck, but I've liked her play pattern for rewarding going wide. The flexibility between mana acceleration and optional impulse draw have been great.

If you need one more cut, I think you could probably swap out Etali. I used to play it, but found the play pattern to be very boom or bust. If I didn't have a Haste enabler, it often ate removal within the turn cycle after it dropped, and never swung out.

I'd agree with Crow's suggestion. I didn't suggest it because I understand how attached people are to their Meld creatures but Hanweir Battlements  ^Meld and Hanweir Garrison  ^Meld are the only meld pair I'd run here personally because each does something the deck wants on its own.

I do stand by my other suggested cuts though and if you're looking to add Hanweir, cut a land for the land and Etali for the creature.

Last_Laugh and Crow_Umbra would you consider adding anything from the Karlov Manor set? I'm thinking Aurelia, Argus Kos, and Tomik

I think you're pretty spot on with all of those Ricccochet, except maybe Tomik. I have kind of mixed feelings on effects liked new Tomik and stuff like Marchesa's Decree. I've tried some of them out in earlier versions of my Isshin deck, but ended up removing them all. Without Isshin on field, my opponents would just tank through the regular triggers, or remove the "pillow" effect.

New Agrus Kos is cool, but I think Nelly Borca, Impulsive Accuser is also worth a look, especially if you're running other Goad effects.

Since you're already running Karazikar, I'd recommend also taking a look at Breena, the Demagogue and/or Firemane Commando to round out your combat control suite. I've really liked Breena, since I play in a fairly aggro go-wide meta. My opponents tend to let her stick around since they benefit enough from her. Once she's big enough she can snipe people pretty easily. Breena or Firemane could probably be swaps for Audacious Thief. Flying for offensive & defense are helpful, & Breena can help grow the rest of your board.

Firemane Commando & Karazikar might get swapped out for New Aurelia & Nelly Borca in my list.

I'm not sure Argus will make the cut. I was eyeballing those other 2 and possibly Warleader's Call. Aurelia feels a bit win more with the amount of creatures you need to swing with because if I have 3-5 creatures swinging then things are probably going my way already. I am light on flyers though so I'm on the fence. Tomik is the one I'm most confident will make the cut for me (not because I think it will trigger, but rather as just a deterrent).