Notes & Combos
If you are wondering if this deck is good against Snake-Eyes - no it's not. It has good chances against most other decks however. Notably, this deck is strong against Tenpai, stun and Kash.
I tried a number of different hand-traps/board breakers in the slots currently occupied by Ash/Bystials/Nibiru, including Evenly/Tactics + Thrust/Lava Golem/Sphere Mode/Belle/CBtG/Veiler/more Bystials/Droll. They all had their issues - mostly due to negative card advantage, being unplayable too often and messing with my normal summon. Ultimately, I settled on this because I wanted to play going second cards that are useful going first while being able to generate/keep even on card advantage.
For my ED, Doom Dragon probably stands out. It switched places with Appo/Unchained Soul of Abomination a few times. Ultimately I setteld on Doomed Dragon for 2 reasons - it can be an extender/removal in some Fiendsmith lines and is sometimes very easy to summon against Snake-Eyes while freeing up my Lovely from the S/T zone. Unicorn's main purpose is as a Rage target when you are fiend locked by Welcome, though the situation only came up a few times.
If you are wondering why I only play 2 Trap Tricks, 2 Butlers and 1 Chandgralier, I have tested 3 Butler, 3 Trap Tricks and every combination of Stovie Torbie/Chandgralier from 1 Stovie Torbie to all 4. The issue I found with the full play set is that I was seeing multiple copies way too often and every time it happens it is rough on my card economy. Butler especially since I have a limited number of trap targets.
The usual endboard you are going for with Fiendsmith lines is Unchained Soul of Rage + Caesar. You go into Lacrima -> Yama -> Search Shavarra -> link into Soul of Rage -> Pop Soul of Rage to Summon Shavarra -> Resummon Soul of Rage with Yama and recycle the appropriate fiend -> Summon Engraver from the Graveyard -> Overlay for Caesar. However, there are other lines depending on your hand and what handtraps you had to get through/play around.
If you open with both Fiendsmith and Lab, you will have to decide on a case-by-case basis how you want to bait out the handtraps. I usually start with the Fiendsmith stuff.
I play 2xTract instead of 1. I don't like opening my only Tract + Lurrie/Engraver every ~23 games.
For changes, I would consider 2 copies of Ice Dragon Prison, 2nd Nib, 1xRollback, Appo, Underworld Goddess and Unchained Soul of Abomination. Also a Beatrice/Rollback package might be good.
Replays
363-654-250
The M1 run was made exclusively with some variant of this deck.
I tried to pick some longer games. There are definitely misplays, but I'm struggling to find games that I actually like watching.
The replay in the list are mostly/all wins, but the actual win rate is probably around 50-60%. I'm just trying to showcase what the deck does.